English (Part – B) (NDA SOLVED PAPER 2020 – II) (51 to 100)

Total Questions: 50

41. Which one of the following statements regarding magnetic field is not correct?

Correct Answer: (c) Magnetic field lines are open curves
Solution:Magnetic field lines are always closed curves because magnetic monopoles do not exist.

42. Which one of the following statements is not correct?

Correct Answer: (b) Diamond is a good conductor of electricity
Solution:Statement (b) is not correct whereas statement (a), (c) and (d) are correct. Diamond is a poor conductor of electricity because here each carbon atom is bonded of four other carbon atoms forming rigid three dimensional structure.

43. How many covalent bonds are present in a Chloropropane molecule having molecular formula,C₃H₂CI?

Correct Answer: (d) 10
Solution:

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 is defined as the number of protons found in the nucleus of every atom of that element.

45. Neutrons were discovered by

Correct Answer: (a) James Chadwick
Solution:Neutrons were discovered by James Chadwick. Neutrons are uncharged particles found within all atomic nucleus.

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

Correct Answer: (b) protons and neutrons only
Solution:Atomic mass of an element is equal to the sum of number of protons and neutrons only. e.g. carbon atom,
proton = 6            nuetron = 6
Atomic mass = 6 + 6 = 12

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

Correct Answer: (b) Cobalt
Solution:Isotope of Cobalt (Co) is used in the treatment of cancer. Cobalt therepy is the medical use of gamma rays from the radioisotope cobalt-60 to treatment of cancer.

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:In some unicellular eukaryotic organisms (e.g Amoeba), cellular nitrogenous waste such as ammonia and excess water are excreted by exosmosis via contractile vacuole. These are special types of vacuoles, which regulates osmotic pressure of cell through osmosis and control water movement across the cell membrane.
When these vacuoles merge with the cell membrane they expel wastes into the external aquatic environment.

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 means the practice of growing two or more crops simultaneously on the same piece of land. In this system, pulses and some oilseeds are grown with maize, sorghum and pearl millet.
It prevents complete loss of crop due to inadequate rain, pests invasion and pathogen infection on a particular crop. Crop rotation involves growing different crops on the same land in the preplanned succession.
Intercropping is the practice of growing more than one crop on the same field at the same time in different row pattern. Mixed farming involves the growing of crops as well as the raising of the livestock. On the same piece of 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:Virus is an acellular structure which is a non-living particle outside of the body of its host. Thus, its lacks protoplasm which is the site of most of the metabolic activities, antibiotics which are effective against bacteria (living prokaryotic cell), are ineffective on viruses.