Free Online Chemistry Science Practice Test Paper

Free Online Chemistry Science Practice Test Paper
1. The element with atomic number 9 resembles in properties with the element having atomic number
(a) 19
(b) 17
(c) 36
(d) 27
Ans. (b)

2.Which one of the following has the smallest size?
(a) Al
(b) AL+
(c) Al+2
(d) Al+3
Ans. (d)

3. The number of electrons in the outer shell of the most stable or inert atoms is
(a) 1
(b) 4
(c) 6
(d) 8
Ans. (d)

4. An atom which has a mass number of 14 and has 8 neutrons is an:
(a) Isotope of oxygen
(b) Isobar of oxygen
(c) Isotope of carbon
(d) Isobar of carbon
Ans. (c)

5. Members of which of the following have similar chemical properties?
(a) Isotope
(b) Isobars
(c) Allotropes
(d) Both isotopes and allotropes
Ans. (a)

6. For an element with atomic number 19, the 19th electron will occupy
(a) L-shell
(b) M-shell
(c) N-shell
(d) K-shell
Ans. (b)

7. A natural phenomenon that supports the experimental conclusion that atoms are divisible is
(a) Allotropy
(b) Radioactivity
(c) Cracking
(d) None of these
Ans. (b)

8. The valency of an element is
(a) The mass of the element displacing 1 part by the mass of hydrogen
(b) The mass of the element combining with 8 parts by mass of oxygen
(c) The number of toms of hydrogen combining with 1 atom of the given element
(d) The number of atoms in 1 molecule of the given element
Ans. (c)

9. The fundamental particles not present in the nucleus of hydrogen atom is
(a) electron
(b) Proton
(c) Neutron
(d) None of these
Ans. (c)

10. The maximum number of electrons that can be accommodated in M Shell of an atom are
(a) 8
(b) 32
(c) 18
(d) 25
Ans. (c)

11. The oil drop experiment by R.A. Mullikan was performed to find
(a) Charge on the neutron
(b) Charge on the electron
(c) Charge on the Proton
(d) None of these
Ans. (b)

12. The experiment which led to the discovery of nucleus was performed by
(a) Goldstein
(b) J.J. Thomson
(c) Dalton
(d) Rutherford
Ans. (d)

13. The electronic configuration of the element with Atomic number 19 is
(a) 2, 8, 7
(b) 2, 9, 8
(c) 2, 8, 8, 1
(d) 2, 10, 7
Ans. (c)

14. An element has electronic configuration 2,8,4. It will be classified as
(a) Metal
(b) Non metal
(c) Metalloid
(d) None of these
Ans. (b)

15. The element with highest electron affinity in the periodic table is
(a) Iodine
(b) Chlorine
(c) Fluorine
(d) Oxygen
Ans. (b)

16. A pH -2 solutions is more acidic than one with pH 6 by a factor of
(a) 4000
(b) 2
(c) 10000
(d) 8000
Ans. (c)

17. Which of these is a pairs of isobar?
(a) 6C12, 8O16
(b) 6C13, 6C14
(c) 20Ca40, 18Ar40
(d) None of these
Ans. (c)

18. In the reaction of Zn + FeSO4 —— ZnSO4 + Fe
(a) Zn gets oxidized
(b) Fe gets oxidized
(c) Zn is oxidized in agent
(d) Zn and Fe both get oxidized
Ans. (a)

19. Which of the following is an example of strong electrolyte?
(a) NH4OH solution
(b) NaOH
(c) CH3COONa
(d) HCN
Ans. (b)

20. The element with atomic number 9 resembles with the element having atomic number
(a) 8
(b) 17
(c) 36
(d) 27
Ans. (b)

21. The elements belonging which group called representative elements?
(a) gp 1 and 2
(b) gp 3 to 12
(c) gp 13 to 18
(d) Element lying at the bottom of periodic table
Ans. (a)

22. Which of the electropositive?
(a) H
(b) Mg
(c) Ca
(d) Si
Ans. (c)

23. With the increase in size in a group
(a) Metallic character decreases
(b) Metallic character increases
(c) Chemical reactivity decreases
(d) Chemical reactivity remains same
Ans. (b)

24. The elements of group 18 are
(a) Halogens
(b) Noble gases
(c) Chalcogens
(d) all caline earth metals
Ans. (b)

25. The properties of the elements, as well as the formula and properties of their compounds depend in a periodic manner on the atomic weights of the elements. This periodic law was given by
(a) J. Lothar Meyer
(b) John A.R. Newlands
(c) Dobemier
(d) D.I. Mendeleev
Ans. (d)

Free PDF Download Chemistry Questions of BHU Medical Entrance

Free PDF Download Chemistry Questions of BHU Medical Entrance
E book  PDF  Exam Containing 16 Questions
These Questions were asked in BHU PMT Entrance
Download NOW 

10+2 level Chemistry Fully Solved for PMT PET IIT JEE

10+2 level SOLVED PAPER. Chemistry For AIEEE, IIT-JEE, PMT, Other State / National Level Engg / Medical Entrance
Fully Solved Question Paper Chemistry
1. Heat of neutralization of strong acid and strong base is constant and equal to:

(a) 10.7 kcal

(b) 13.7cal

(c) 23.7 kcal

(d) 33.7 kcal

Ans. (b)

2. The first law of thermodynamics is represented by:

(a) ΔE=ΔQ÷ΔW

(b) ΔE=ΔQ+W

(c) ΔE=Q+W

(d) ΔE=Q-W

Ans. (c)

3. The metal that forms a self protecting film of oxide to prevent corrosion is:

(a) Al

(b) Au

(c) Ag

(d) Cu

Ans. (a)

4. H₂O₂ is reducing agent in the reaction:

(a) Ag₂O+ H₂O₂ → 2Ag+ H₂O+O₂

(b) 2K1+ H₂O₂ → 2KOH+ I₂

(c) H₂O₂+ SO₂ → H₂SO₄

(d) PbS + 4H₂O₂ → PbSO + 4H₂O

Ans. (a)

5. The hybridization shown by six carbon atoms in benzene is:

(a) 3sp³ 3sp

(b) 3sp³ 3sp²

(c) 3sp³ sp²

(d) 6sp²

Ans. (d)



6. The molarity of a solution containing 5 g of NaOH in 250 mL solution:

(a) 0.5

(b) 1.0

(c) 1.5

(d) 2.0

Ans. (a)

7. A gas expands isothermally against a constant external pressure of 1 atmosphere from a volume of 10 dm³ to a volume of 20 dm³. In this process it absorbs 800 J of thermal energy from its surroundings. The ?U for the process in Joule is:

(a) +113J

(b) -113J

(c) -213J

(d) +313J

Ans. (c)

8. The most stable is:

(a) NaH

(b) RbH

(c) KH

(d) LiH

Ans. (d)

9. Nitrobenzene and hydrogen in presence of zinc and HC1 combines to form:

(a) Azobenzene

(b) Benzene

(c) Azoxybenzene

(d) Aniline

Ans. (d)

10. Ethyl alcohol is soluble in water due to:

(a) Acidic nature

(b) Basic nature

(c) Formation of hydrogen bond

(d) Dissociation in water

Ans. (c)

11. In a chemical equilibrium rate constant of forward reaction is 75⁹ x10^-4 and the equilibrium constant is 1.5. The rate constant of backward reaction is

(a) 2.5x10⁴

(b) 5x10^-4

(c) 2.5 x10^-4

(d) 5 x 10⁴

Ans. (b)



12. Conversion of starch into maltose takes place by the enzyme:

(a) Invertase

(b) Maltase

(c) Diastase

(d) Zyrase

Ans. (c)

13. The oxide which forms dimer is:

(a) N₂O₅

(b) N₂O

(c) NO₂

(d) N₂O₃

Ans. (c)

14. The hardest naturally occurring substance is:

(a) Iron

(b) Graphite

(c) Diamond

(d) Astatine

Ans. (c)

15. Wax belongs to the class:

(a) Alcohol

(c) Ether

(b) Ester

(d) Acid

Ans. (b)

16. The chloramphenicol is an example of:

(a) Antiseptic

(b) Antibiotic

(c) Analgesics

(d) Antipyretics

Ans. (b)

17. The heat of formation of CO₂ is 95 kcal. The amount of carbon which on burning will evolve 1000 kcal is

(a) 12.63 g

(b) 17.95 g

(c) 126.3 g

(d) 179.5 g

Ans. (c)

18. Normality of orthophosphoric acid having purity of 70% by weight and specific gravity 1.54 is:

(a) 11N

(b) 22N

(c) 33N

(d) 44N

Ans. (c)

19. Chloroform and conc. HNO3 reacts to produce:

(a) CHC1₂HNO₃

(c) CC1₃NO₂

(b) CHC1₂NO₃

(d) CHC1NO₃

Ans. (c)



20. Gold number is associated with:

(a) Protective colloids

(b) Purple of cassius

(c) Amount of pure gold

(d) Electrophoresis

Ans. (a)

21. The number of double bonds in gammexane is

(a) 0

(b) 1

(c) 2

(d) 3

Ans. (a)

22. Amino acids are the building blocks of:

(a) Fats

(b) Vitamins

(c) Carbohydrates

(d) Proteins

Ans. (d)

23. The number of atom in 4.25 g of NH₃ is:

(a) 2.054 x 10²³

(b) 3.034 x 10²³

(c) 3.044 x 10²³

(d) 6.023 x 10²³

Ans. (d)

24. The conjugate acid of NH₃ is:

(a) NH

(b) NH₂OH

(c) NH₃

(d) N₂H₄

Ans. (a)

25. The first ionisation potential is maximum for:

(a) Lithium

(b) Hydrogen

(c) Iron

(d) Uranium

Ans. (b)

26. Adiabatic process involves:

(a) ΔE=0

(bΔV=0

(c)ΔW=0

(d) Δq=0

Ans. (d)

27. Which of the following explains the sequence of filling the electrons in different shell?

(a) Aufbau principle

(b) Hund’s rule

(c) Octet rule

(d) All of the above

Ans. (a)

28. The rate of reaction depends upon:

(a) Molar concentration

(b) Atomic mass

(c) Equivalent mass

(d) None of the above

Ans. (a)

29. The purest form of iron is:

(a) Pig iron

(b) Wrought iron

(c) Steel

(d) None of these

Ans. (b)

30. The largest size of the ion is:

(a) CF

(b) Ca₂

(c) K

(d) S₂

Ans. (d)

31. The empirical formula of a compound is CH₂O. Its molecular weight is 180. The molecular formula of the compound is:

(a) C₃H6O₃

(b) C₆H₁₂O₆

(c) C₄H₈O₄

(d) C₅H₁₀O₅

Ans. (b)

32. The Bohr’s orbit radius for the hydrogen atom (n =1) is approximately Q530 Å. The radius for the first excited state (n = 2) orbit is

(a) 1.08 Å

(b) 2.12 Å

(c) 3.24 Å

(d) 4.36 Å

Ans. (b)

33. Roasting of an ore is done in:

(a) Presence of air

(b) Absence of air

(c) Vacuum

(d) None of these

Ans. (a)

34 The dissociation constant of two acids HA₁ and HA₂ are 3.0 x 10^-4 and 1.8 x 10^-5 respectively. The relative strength of acid HA₁: HA₂ is:

(a) 16:1

(b) 1:16

(c) 4:1

(d) 1:4

Ans. (c)

35. Natural rubber is a polymer of:

(a) 1, 4-butadiene

(b) Ethylene

(c) Isoprene

(d) Terephthalic acid

Ans. (c)

36. The alkyl halide is converted into alcohol by:

(a) Elimination

(b) Halogenations

(c) Addition

(d) Substitution

Ans. (d)

37. The gas used in air ships is:

(a) He

(b) Ne

(c) Ar

(d) Xe

Ans. (a)

38. An aqueous solution of ammonium acetate is:

(a) Acidic

(b) Basic

(c) Neutral

(d) None of these

Ans. (c)

39. The highest melting halide is:

(a) NaF

(b) NaCl

(c) NaBr

(d) Nal

Ans. (a)

40. The pH of a 10’° molar solution of HCl in water is

(a) 6.0

(b) 7.0

(c) 10

(d) 14

Ans. (b)

Exam Questions And Quiz Test Inorganic Chemistry

Exam Questions And Quiz Test Inorganic Chemistry
These Objective Solved Questions are very useful for Quiz on Chemistry andjob recruitment exams Like PSC UPSC NDA etc

1. When a little sulphur in a spoon is heated, it burns with a blue flame which slowly disappears after some time and we can feel a pungent odour. This pungent odour is due to
(a) Carbon dioxide
(b) Sulphur dioxide
(c) Sulphur gas
(d) Sulphuric acid
Ans. (b)

2. The formula of Baking soda is
(a) Sodium carbonate
(b) Sodium bicarbonate
(c) Calcium carbonate
(d) Sodium hydroid
Ans. (b)

3. Which of the foll6wing is a weak base?
(a) NaOH
(b) KOH
(c) NH4OH
(d) None of these
Ans. (c)

4. A basic salt that is used in daily life is
(a) Sodium acetate
(b) Sodium chloride
(c) Ammonium sulphate
(d) Sodium carbonate
Ans. (b)

5. Which of the following is spread on icy roads to melt ice in cold countries?
(a) Sodium bicarbonate
(b) Rock salt
(c) Sodium hydroxide
(d) None of these
Ans. (b)

6. Which of the following is a hydrated salt?
(a) Ca(OH) 4
(b) MgCO3
(c) MgSO.7H2O
(d) BaSO4
Ans. (c)

7. Calcium phosphate can be obtained by reacting calcium hydroxide with
(a) Phosphoric acid
(b) Nulphuric acid
(c) Nitric acid
(d) Both (b) and (c)
Ans. (a)

8. Epsom salt is
(a) CuSO4
(b) CaSO4
(c) MgSO4
(d) Na2SO4
Ans. (c)

9. What happens when hydrated copper sulphate is heated?
(a) It becomes colourless
(b) It turns into anhydrous salt
(c) It loses water of crystallization
(d) All of the above
Ans. (d)


10. Which of the following statement is correct?
(a) Only organic acids conduct electricity
(b) Only mineral acids conduct electricity
(c) All acid solutions, whether organic acids or mineral acids, conduct electricity
(d) None of these
Ans. (c)

11. Which of the following acid is also known as battery acid that is used in car batteries?
(a) H2SO4
(b) HCI
(c) HNO3
(d) H3PO4
Ans. (a)


12. What happens to the colour of litmus paper when a drop of acid falls on it?
(a) Colour fades
(b) From blue it turns red
(c) From red it turns blue
(d) Remains unchanged
Ans. (b)

13. The term ‘pH’ comes from
(a) Hydrogen purity
(b) Pure Hydrogen
(c) Hydrogen power
(d) Purity of Hydrogen
Ans. (c)

14. The pH of 1 x 10-8 M HC1 solution is
(a) 8
(b) 7
(c) 6
(d) None of the above
Ans. (d)

15.While mixing H2SO4 with water which of the• following precautions should be taken?
(a) Never add acid to water
(b) Never add water to acid
(c) Add the lighter heavier liquid
(d) Avoid sunlight
Ans. (b)


16. Which of the following may be regarded as weak electrolytes?
(a) NaC1
(b) CH3COONa
(c) HC1
(d) CH3COOH
Ans. (d)

17. The pH of three solutions A, B, C is 6, 4, 8 receptivity which of the following is the correct option?
(a) A>B>C decreasing acidic strength
(b) C>B>A increasing acidic strength
(c) B>A>C is decreasing acidic strength
(d) C>B>A decreasing acidic strength
Ans. (c)

18. An aqueous solution of NaCl is
(a) Acidic
(b) Basic
(c) neutral
(d) Either acidic / basic
Ans. (c)

19. ‘Alum’ is an example of
(a) Single salt
(b) Double salt
(c) Acids
(d) None of above
Ans. (b)

20. All salts are
(a) Strong electrolytes
(b) Weak electrolytes
(c) Non electrolytes
(d) Either weak or strong
Ans. (d)

21. An aqueous solution of CH3COONa is
(a) Acidic
(b) Basic
(c) Amphitricha
(d) Either Acklic/Basic
Ans. (b)

22. A pH -2 solutions is more acidic than one with pH 6 by a factor of
(a) 4000
(b) 2
(c) 10000
(d) 8000
Ans. (c)

23. Electro refining which is based on phenomenon of Electrolysis where
(a) Impure metal is made anode and pure metal is cathode
(b) Impure metal is cathode and pure metal is anode
(c) Pure metal makes both anode and cathode
(d) None of the above

24. Which of the following is an example of strong electrolyte?
(a) NH4OH solution
(b) NaOH
(c) CH3COONa
(d) HCN
Ans. (b)

25. The loss of water of crystallization to the atmosphere by a compound is termed
(a) deliquescence
(b) dehydration
(c) efflorescence
(d) hydrolysis
Ans. (c)

Free online Chemistry Test for Exams containing Solved Questions

Free online Chemistry Test for Exams containing Solved Questions
Very useful for medical entrance Tests like PMT as well as Engineering Entrance Tests Like AIEEE


1. Noble gases exist as individual
(a) Atoms
(b) Molecules
(c) Ions
(d) Compounds
Ans. (a)


2. Electropositive atoms tend to form
(a) Negative ions
(b) Positive ions
(c) Covalent bonds
(d) Metallic bonds
Ans. (b)


3. Electrovalent compounds are usually
(a) Solids with low melting points solids with
(b) High melting points
(c) Volatile liquids
(d) Organic compounds



4. In electrovalence
(a) Molecules lose electrons forming atoms
(b) Molecules gain electrons forming atoms
(c) Atoms share electrons
(d) Atoms lose or gain electrons forming ions
Ans. (d)


5. A double bond between two carbon atoms is formed by
(a) The transfer of two electrons from one carbon atom to the other
(b) The transfer of one electron from one carbon atom to the other
(c) Two shared electron pairs
(d) The sharing of two electrons
Ans. (c)

6. Which of the following is a non-polar molecule?
(a) NH3
(b) HC1
(c) CCl4
(d) H2O
Ans. (c)

7. The bonding in ammonium chloride
(a) is covalent only
(b) is electrovalent only
(c) Consists of three covalent nitrogen- hydrogen bonds and an electrovalent bond between the ammonia molecule and the chlorine atom.
(d) Consist of four covalent nitrogen-hydrogen bonds and one electrovalent bond between the ammonium ion and chloride ion.
Ans. (d)

8. Which amongst the following has smallest size?
(a) Na
(b) Al
(c) Na+
(d) Al3+
Ans. (d)


9. Which amongst the following can lose 2 electrons to acquire the configuration of argon?
(a) N
(b) Mg
(c) Ca
(d) Be
Ans. (c)


10. Two electronegative atoms combine to form
(a) Ionic bond
(b) Covalent bond
(c) Coordinate bond
(d) Can’t be predicted
Ans. (b)


11. An element with low ionization energy combines with an element having high electron affinity to form
(a) Ionic bond
(b) Covalent bond
(c) Dative bond
(d) None of these
Ans. (a)


12. The actual formula of sodium chloride is
(a) NaC1
(b) Na+ C1-
(c) (Na+ Cl-)n
(d) NanCln
Ans. (c)

13. Which of these has a triple covalent bond?
(a) PH3
(b) CO2
(c) A1C13
(d) C2H2
Ans. (d)

14. The number of covalent bonds in ethylene is
(a) 2 double bonds, 2 single bonds
(b) 2 double and 4 single bonds
(c) 2 single and 2 double bonds
(d) 1 double and 4 single bonds
Ans. (d)

15. When an alkali metal combines with halogen, it will form
(a) Always covalent bond
(b) Always ionic bond
(c) May be covalent or ionic
(d) Will not combine at all
Ans. (b)

16. An element ‘X’ belongs to group 11 while an element ‘Y’ belongs to group 17 of the periodic table. They are expected to form
(a) An ionic compound with formula X Y
(b) An ionic compound with formula XY2
(c) A covalent compound with formula XY2
(d) A covalent compound with formula X2Y
Ans. (b)

17. Which amongst the following will not conduct electricity?
(a) NaC1
(c) CaF2
(b) MgC12
(d) C6H12O6
Ans. (d)

18. Which amongst the following has a polar covalent bond?
(a) NaC1
(b) NH3
(c) O2
(d) CaO
Ans. (b)

Practice Chemistry Questions on Atoms

Practice Chemistry Questions on Atoms
Chemistry Quiz - Questions & Answers on Atoms
1. The fundamental particles not present in the nucleus of hydrogen atom is
(a) electron
(b) Proton
(c) Neutron
(d) None of these
Ans. (c)


2. The maximum number of electrons that can be accommodated in M Shell of an atom are
(a) 8
(b) 32
(c) 18
(d) 25
Ans. (c)


3. The oil drop experiment by R.A. Mullikan was performed to find
(a) Charge on the neutron
(b) Charge on the electron
(c) Charge on the Proton
(d) None of these
Ans. (b)


4. The experiment which led to the discovery of nucleus was performed by
(a) Goldstein
(b) J.J. Thomson
(c) Dalton
(d) Rutherford
Ans. (d)


5. The electronic configuration of the element with Atomic number 19 is
(a) 2, 8, 7
(b) 2, 9, 8
(c) 2, 8, 8, 1
(d) 2, 10, 7
Ans. (c)


6. An element has electronic configuration 2,8,4. It will be classified as
(a) Metal
(b) Non metal
(c) Metalloid
(d) None of these
Ans. (b)


7. Amongst element X (2, 8, 6) and Y (2, 8, 8) which is more reactive and why?
(a) X because it is a metal
(b) Y because it is non metal
(c) Because it has 6 valence electrons
(d) Y because it is gas
Ans. (c)

8. Which of these is a pairs of isobar?
(a) 6C12, 8O16
(b) 6C13, 6C14
(c) 20Ca40, 18Ar40
(d) None of these
Ans. (c)



9. The e/m value for cathode rays
(a) Varies with the nature of the gas
(b) Does not vary with the nature of gas
(c) Could not be determined by J.J. Thomson
(d) Both (b) and (c) are correct
Ans. (b)


10. Isotopes differ in
(a) no. of electrons
(b) no. of protons
(c) no. of neutrons
(d) Chemical reactivity
Ans. (c)

Practice Objective Chemistry Test on Periodic Table

Practice Objective Chemistry Test on Periodic Table
Periodic Table of the Elements Quiz - Test Your Chemistry


1. An element has 12 neutrons in its nucleus. To which group of the periodic table it will belong?
(a) 1
(b) 2
(c) 6
(d) Impossible to predict
Ans. (d)


2. The element with atomic number 9 resembles in properties with the element having atomic number
(a) 19
(b) 17
(c) 36
(d) 27
Ans. (b)

3. Atomic number and not the atomic weight is the fundamental property of an element was enunciated by?
(a) Dalton
(b) Bohr
(c) Mosley
(d) Mendeleev
Ans. (c)


4. Elements in a period have same
(a) Number of valence electrons
(b) Valency
(c) Number of shells
(d) Volume
Ans. (c)


5. Elements belonging to the same group have similar properties because
(a) They have similar electronic configuration of the outermost shell
(b) Their atomic numbers go on increasing as we move down the group
(c) all of them the metallic elements
(d) None of the above
Ans. (a)


6. The atoms of elements belonging to the same group of periodic table have the same
(a) Number of protons
(b) Number of electrons
(c) Number of neutrons
(d) Number of electrons in the outermost shell
Ans. (d)


7. Which of the following is the correct order of relative sizes?
(a) I->I+>I
(b) I->I+>I+
(c) I>I+>I-
(d) I+>I->I
Ans. (b)


8. On moving horizontally across a period, the number of electrons in the outermost shell increases from- to-
(a) 2, 8
(b) 2, 18
(c) 1, 8
(d) 1, 18
Ans. (c)



9. Which of the following hydroxides is most basic?
(a) Be(OH)2
(b) Ba(OH)2
(c) Ca(OH)2
(d) Mg(OH)2
Ans. (b)


10. The element with smallest size in the 4th period is
(a) Chlorine
(c) Fluorine
(b) Iodine
(d) Bromine
Ans. (d)


11. The most metallic element in the fifth period is
(a) Silver
(b) Rubidium
(c) Gold
(d) Rhodium
Ans. (b)






12. Element ‘A’ has Electronic configuration 2,7 ‘B’ has configuration 2,8,6, ‘C’ has configuration 2,8,8 while ‘D’ has 2,8,7. Which element will show similar chemical properties?
(a) A and C
(b) A and D
(c) B and C
(d) B and D
Ans. (b)


13. Law of Triad was proposed by
(a) Newland
(b) Gay Lussac
(c) Mendeleev
(d) Dobereiner
Ans. (d)

14. Third period of the periodic tables contains the following number elements.
(a) 2
(b) 18
(c) 8
(d) 32
Ans. (c)


15. The element with electronic configuration 2, 8,6is
(a) Metallic with valency 2
(b) Non-metallic with valency 2
(c) Metalloid with valency 2
(d) None of these
Ans. (b)