It is B nevermind I thought it was c but it wasn't.
Answer:
The H in the carboxyl group.
Explanation:
Acetic acid can be written as CH₃COOH, where -COOH is the functional group carboxyl, responsible for the acidity of organic acids. The H in the carboxyl group is the one that is donated in the acid reaction.
CH₃COOH(aq) + H₂O(l) ⇄ CH₃COO⁻(aq) + H₃O⁺
Acetic acid is a weak acid, so just a small fraction of the molecules undergo this reaction to donate their hydrogen.
