Final answer:
Among the options given, the amine functional group is polar and acts like a base because it contains a nitrogen atom able to accept protons.
Step-by-step explanation:
The functional group that is polar and acts like a base among the given options is the amine group. Amine functional groups contain a nitrogen atom with a lone pair of electrons, which makes them basic as they can accept protons. This is distinct from aldehydes, ketones, and carboxylic acids, which have different properties. Aldehydes and ketones both contain a carbonyl group, but neither behaves as a base. Meanwhile, carboxylic acids are acidic rather than basic due to the presence of a hydroxyl group attached to the carbonyl carbon, which can donate a proton in aqueous solution.