Final answer:
A carboxylic acid is an organic compound that contains the carboxyl functional group. CH₃CH₂COOH is a carboxylic acid, while the other options are not.
Step-by-step explanation:
A carboxylic acid is an organic compound that contains the carboxyl functional group. The general formula for a carboxylic acid is R-COOH. The carbon atom of the carboxyl group may be attached to a hydrogen atom or to a carbon chain. When naming a carboxylic acid, change the -e at the end of the name of the alkane to -oic acid.
The compound CH₃CH₂COOH is propionic acid, which is a carboxylic acid. The other options, CH₃CH₂OCH₃, CH₃CH₂CH₂OH, and CH₃CH₂CHO, are not carboxylic acids.