ANSWER :-
(a ) A ketone functional group is present in the compound CH3COCH2CH2CH2CH3.
(b ) A carboxylic acid functional group is present in the compound CH3CH2CH2COOH.
(c ) An aldehyde functional group is present in the compound CH3CH2CH2CH2CHO.
(d ) An alcohol functional group is present in the compound CH3CH2OH