What is the general structure of a carboxylic acid?

The structure of a carboxylic acid is accurately represented by the formula R-C=O-OH. In this structure, "R" denotes a hydrocarbon chain or substituent, while "C=O" represents a carbon atom double-bonded to an oxygen atom, which is characteristic of carbonyl groups. The "-OH" group, known as a hydroxyl group, is attached to the same carbon atom that is double-bonded to the oxygen. This specific arrangement of a carbonyl group adjacent to a hydroxyl group defines carboxylic acids and gives them their acidic properties.

In contrast, the other options do not reflect the structure of carboxylic acids. The structure R-C=O-R suggests an ether or ketone, as it indicates that two carbon groups are attached to the carbonyl carbon without the presence of a hydroxyl group. The option R-C-O-R' suggests an alcohol or ether structure, which lacks the carbonyl group entirely. Lastly, R-NH₂ denotes an amine structure, which is unrelated to carboxylic acids. Thus, option A is the only correct representation of a carboxylic acid's structure.