(a) chlorofluorocarbon compounds

(b) carbon monoxide

(c) methane

(d) pesticides

Correct option – ( a )

Explanation for correct option – in the stratosphere  chlorofluorocarbon compounds are broken down by the ultraviolet rays . Break down of chlorofluorocarbon compounds results in release of chlorine which interacts with ozone layer and is the reason for its depletion

Explanation for incorrect option – carbon monoxide , methane and pesticides do not contain chlorine which can react with ultra violet rays and cause depletion of ozone layer

Hence correct option is chlorofluorocarbon compounds .