Which of the following acid does NOT contain -COOH group?

Lactic acid is 2-hydroxypropanoic acid, which has the formula $CH_3CH(OH)COOH$. It contains a -COOH group.

Picric acid is 2,4,6-trinitrophenol, which has the formula $C_6H_2(OH)(NO_2)_3$. It contains a phenolic -OH group but does not contain a -COOH group.

Benzoic acid is $C_6H_5COOH$. It contains a -COOH group.

Oxalic acid is ethanedioic acid, $HOOC-COOH$. It contains two -COOH groups.

Therefore, picric acid does not contain a -COOH group.

Answer: Picric acid