Fill in the blanks and rewrite the completed statements :
(1) ……………. gas, used for refrigeration and air conditioning, destroys the ozone layer.
(2) Air becomes ……………. at higher altitudes.
(3) ………….. of land is reduced if green trees and bushes are grown in it.
(4) 16th September is celebrated as ………. Day all over the world.
(5) ………….. is the layer of air that surrounds the earth.
(6) ……………. occupies the largest part of the earth’s surface.
(7) Gases are not found in the …………… and beyond.
