Regarding the Structures of Amino Acids, Which, If Any, of the Following

Multiple Choice

Regarding the structures of amino acids, which, if any, of the following statements is incorrect?

A) The general formula for a nonionised amino acid is H₂N-CH(R) -COOH, that is, a central carbon atom is linked to an amino group, a carboxyl group, a hydrogen atom, and a side chain, R.
B) The identity of the amino acid is determined by the side chain that is connected to the central carbon atom.
C) The side chain of an amino acid is based on a branch that contains one or more carbon atoms
D) Proline is unique in having a side chain that is connected to both the central carbon and also to the nitrogen atom of the amino group.