All Amino Acids Have the Same General Structure

All amino acids have the same general structure:

A) a central R-group, linked to a basic amino group and an acidic carboxyl group.
B) an amino group, a carboxyl group and a number of different R-groups, joined to a central carbon atom.
C) a central carbon atom attached to an amino group, a carboxyl group and one of 20 different ribose groups.
D) an amino group, a carboxyl group and one of a variety of different side-chain groups, bonded to a central carbon atom.
E) an amino acid group and a carboxyl group linked through an R-group to form a linear molecule.