Question

a molecule consisting of a carbon chain, with 4 to 24 carbons, with a methyl group on one end and a carboxyl group on the opposite end is which of the following?
amino acid
fatty acid
glycerol
protein

Explanation:

A fatty acid has a carbon - chain with typically 4 - 24 carbons, a methyl group ($-CH_3$) at one end and a carboxyl group ($-COOH$) at the other end. Amino acids have an amino group and a carboxyl group but their structure is more complex and not just a simple carbon - chain with these end - groups. Glycerol is a polyol and has hydroxyl groups. Proteins are polymers of amino acids.

Answer:

B. Fatty acid