Assertion: Chiorofluorocarbons are responsible for ozone depletion.
Reason: Ozone level decreases by as much as 67% every year.

Options

A. If both assertion and reason are true reason is the correct explanation of assertion
B. If both assertion and reason are true but reason is not the correct explanation of assertion
C. If assertion is true but reason is false
D. If both assertion and reason are false.

Answer

B

Explanation

Both assertion and reason are true but reason is not the correct explanation of assertion . A slight thinning of ozone layer occurs naturally for a few months every year over Antarctica . It decreases by `67%` every year. The primary chemicals responsible for ozone depletion are a group of chlorine containing compounds called chloroflurocarbons (CFCs), used as coolants in air conditions and refrigerators (freon) and propellants for aerosol cans and form blowing agents for insulation and packaging and also as solvents. Besides halons, methyl bromide , methyl chloroform. carbon tetrachloride and nitrous oxide are also responsible for `O_(3)` loss. After their release into troposphere, `CFCs` and other chlorine containing compounds go to stratosphere where these are broken down by UV-radiations releasing chlorine. Similarly bromine is released by breakdwon of halons and methyl bromide. The sunlight catalyzes the chemical reaction by which chlorine or bromine and thus single chlorine or bromine atom can breakdwon many thousands of `O_(3)` molecules.