General Ability NDA/NA Solved Paper 2020-I (51-100)

Total Questions: 50

41. Which one ofthe following statements regarding magnetic field is NOT correct?

Correct Answer: (c) Graphite is a good conductor of electircity
Solution:

Magnetic field has both direction and magnitude, the magnetic field lines are closed curves and no two magnetic field lines are found to cross each other.

42. How many covalent bonds are present in a Chloropropane moleculehaving molecular formula, C₂H₇CI?

Correct Answer: (d) 10
Solution:

Diamond is bad conductor of electricity. Electric current is due to flow of free electrons but in diamond four other carbon atoms are covalently bonded hence no free electrons are available to conduct electric current.

43. Which one of the following statements is NOT correct?

Correct Answer: (b) Diamond is a good conductor of electricity
Solution:

Chloropropane molecule with molecular formula C₃H₇CI contains ten covalent bonds. In covalent bonds electron pairs are shared between atoms.

44. Which one of the following is the most fundamental characteristic of an element?

Correct Answer: (b) Atomic number
Solution:

Atomic number is the most fundamental characteristic of an element. It defines number ofprotons in that element. Elements are arranged in order of atomic number in the periodic table.

45. Neutrons were discovered by

Correct Answer: (a) James Chadwick
Solution:

Neutrons are subatomic particles that reside inside the nucleus of an atom along with proton. It contains neutral charge and 1 a.m.u.. Neutrons were discovered by James Chadwick in 1932.

46. Atomic mass of an element is equal to the sum of number of

Correct Answer: (b) protons and neutrons only
Solution:

The atomic mass of an element is equal to the sum of the number of protons and neutrons in the element; thus, option (b) is correct.

47. Which one of the following element's isotope is used in the treatment of cancer?

Correct Answer: (b) Cobalt
Solution:

Isotope of cobalt is used in the treatment of cancer. Cobalt-60 is used in radiotherapy machines produce gamma rays. These gamma rays are focussed on patient's body to target tumor tissues.

48. Which one of the following cell organelles may play a role in expelling excess water and wastes in case of unicellular organisms?

Correct Answer: (b) Vacuole
Solution:

Vacuole plays an important role in expelling ofexcess water and wastes in case of unicellular organisms. Vacuole in multi-cellular organisms also play additional role of storage, ingestion, excretion etc.

49. Which one of the following terms describes the practice of growing two or more crops simultaneously on the same piece of land?

Correct Answer: (b) Mixed cropping
Solution:

Mixed cropping is the practice of growing two or more crops simultaneously on the same land.

50. Which one of the following statements is correct about effects of antibiotics on viruses?

Correct Answer: (c) Viruses do not possess metabolic pathways on which antibiotics can function, whereas bacteria have such pathways
Solution:

Antibiotics work by changing or altering any important metabolic pathway in bacteria. Different types of antibiotics act on different pathways to kill or inhibit
bacterial growth. Viruses on the other hand do not possess metabolic pathways on which antibiotics can act. These antibiotics thus are of no use for viral infection.