Amino acids differ from one another by the that is present
a. amino group
b. carboxyl group
c. r group
d. r plasmid
e. core group

C. R group

Explanation:

Amino acids are the monomers for proteins. Various amino acids are joined together by peptide bonds to form polypeptides.

All standard amino acids have a central chiral carbon atom to which four functional grouped are bonded. All the amino acids have one carboxyl group, one amino group and one hydrogen atom bonded to the central carbon atom.

However, the chemical nature of the "R group" differentiates various amino acids. For example, alanine has a "CH3" group as an R group while glycine has one more hydrogen atom as its R group.