What happens to the buffering capacity when a buffer is highly diluted?
Decreases correctly describes the effect or change asked about in this question. In pH and Buffer, understanding cause-and-effect relationships is essential for predicting biological outcomes. Decreases occurs because of specific molecular interactions, thermodynamic principles, or regulatory mechanisms that govern this biological process. The other options (Increases, Remains the same, and Becomes zero) describe either opposite effects, effects that occur under different conditions, or changes associated with unrelated processes.
Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 2