(i) The ozone layer present in the stratosphere acts as an ultraviolet absorbant thus protecting the earth from its harmful effect.

(ii) Depletion/destruction of ozone layer is primarily caused by `CFCs` (Chlorofluorocarbons) and halons(halocarbons `C_xF_x Br_x`)

(iii)` CFCs` are heat transfer agents used in refrigerators, air conditioners, fire extinguishers.

(iv) Halons are antifire agents used in fire extinguishes.

(v) The `CFCs` react with ozone and thus cause thining of ozone layer which permits more UV radiations to reach the surface of earth.