Question

part a each amino acid is composed of a central carbon that forms covalent bonds with four other atoms/molecules. these atoms/molecules include each of the following except which one? an amino group an a group a carboxyl group an r group a hydrogen atom

Explanation:

The structure of an amino acid consists of a central carbon (alpha - carbon) bonded to an amino group ($-\text{NH}_2$), a carboxyl group ($-\text{COOH}$), a hydrogen atom ($-\text{H}$), and an R group (the side chain which varies among different amino acids). There is no "A group" in the standard structure of an amino acid.

Answer:

B. an A group