(a) If oxygen disappear from the atmosphere then—

i. There will be no life on the earth.

ii. Burning will be not possible due to disappear of oxygen.

iii. Plants and animals consume oxygen for respiration. If there is no oxygen then there will be no plant and animal life.

(b) Nitrogen does not support burning. No nitrogen means that things will burn fast. If there is no nitrogen humans will be dehydrated quickly. The flow of nitrogen cycle will also disturb and the growth of plants will decrease, even cause the death of plants.

(c) Animals produce carbon dioxide. Carbon dioxide is needed by the plants for photosynthesis. If there is no carbon dioxide then plants are not able to make their food due to which there will be no plants and animals as animal depends upon the plants for food.