If a protein has a dissociation equilibrium constant (Kd) of 10^-9 M, what does this suggest about its affinity for the ligand?

• A. The protein has a very high affinity for the ligand.
• B. The protein binds to the ligand at a rate of 10^-9 M/s.
• C. The protein has a very low affinity for the ligand.
• D. The protein does not bind to the ligand.

Answer: (A)