Final answer:
The weak acid among the given compounds is phenol (C). Phenol is an organic compound that contains a hydroxyl group and can donate a proton to a base, but does not fully dissociate in water.
Step-by-step explanation:
The weak acid among the given compounds is phenol (C). Phenol is a type of organic compound that contains a hydroxyl group (-OH) attached to an aromatic ring. The presence of the hydroxyl group makes phenol a weak acid because it can donate a proton (H+) to a base, but does not fully dissociate in water.