The naturally occurring amino acid that contains only one basic functional group in its chemical structure is

Step 1: Assessing Functional Groups — Naturally occurring $\text{L-amino acids}$ contain at least one amino and one carboxyl group at the $\alpha$-position.

Step 2: Side Chain Analysis — Lysine, Arginine, and Histidine have additional basic groups in their side chains. Asparagine has an amide side chain which is not basic.

Step 3: Conclusion — In asparagine ($H_2N-CO-CH_2-CH(NH_2)COOH$), the $\alpha\text{-amino}$ group is the only basic functional group. Correct option is (c).

Remember: Amides are very weak bases compared to amines.