What is the name of the class of compounds having functional group -COOH? 

Carboxylic acids 

The correct answer is option 4. Carboxylic acids.

The name of the class of compounds having the functional group -COOH is Carboxylic acids. The functional group -COOH, also known as the carboxyl group, consists of a carbonyl group (C=O) and a hydroxyl group (-OH) attached to the same carbon atom. Carboxylic acids are organic compounds characterized by this carboxyl group, and they are named based on the presence of this functional group.

Therefore, the correct answer is Carboxylic acids.