Which two functional groups are always found in amino acids?

a) Carbonyl and amino groups.

b) Carboxyl and amino groups.

c) Amino and sulfhydryl groups.

d) Hydroxyl and carboxyl groups.

• A. Carbonyl and amino groups.
• B. Carboxyl and amino groups.
• C. Amino and sulfhydryl groups.
• D. Hydroxyl and carboxyl groups.