Among the following compounds most basic amino acid is

Step 1: Identifying Side Chain Basicity — Amino acids vary based on the basicity of their side (R) groups. Acidic residues like Asp are excluded.

Step 2: Comparing Basic Amino Acids — Lysine has a primary amino side chain ($\text{p}K_a \\approx 10.5$), while Histidine has an imidazole group ($\text{p}K_a \\approx 6.0$).

Step 3: Conclusion — Therefore, lysine is significantly more basic than histidine, serine, and asparagine. Correct option is (b).

Key Point: Arginine would be even more basic if included, due to its highly resonance-stabilized guanidino group.