Classify each organic compound based on the functional group it contains

Answer: Carboxylic acid, Ester,Ether and Alcohol
Explanation: Carboxylic acid is the one which has COOH group which includes carbonyl group and OH.
And ester is a derivative of Carboxylic acid which has COOR . It has -OR alongwith Carbonyl group.
And ether has C-O-C skeleton
And alcohol has R-OH as a general formula.