What makes amino acids unique from fatty acids and sugars?

C. Amino acids contain nitrogen; fatty acids and sugars do not.

Amino acids are unique among these biomolecules because they contain an amino group (–NH2) which includes nitrogen. In contrast, fatty acids and sugars do not have nitrogen in their structure. While it's true that amino acids are building blocks of proteins, fatty acids can also contribute to larger molecules (like lipids), and both fatty acids and sugars can provide energy to the body. Therefore, C is the most accurate option highlighting the unique aspect of amino acids.