Question

Which of the following functional groups defines a carboxylic acid?

a) -OH
b) =O
c) -PO4
d) -COOH

Answer 1

Correct option D -COOH

Carboxylic acid example - Acetic acid
It's formula is CH3COOH

It has functional group -COOH

So it's D

Hope This Helps You!

Answer 2

last choice is the answer.

the name should give us a hint. 

carboxylic acid----> carboxylic means carbon with oxygens (CO or COO) and acid means it has hydrogens (H)