Renal threshold of drug means -
Ans. is 'a' i.e., Drug concentration above which it appears in urine Renal Thresholdo The renal threshold is the concentration of a substance dissolved in the blood above which the kidneys begin to remove it into the urine. When the renal threshold of a substance is exceeded, reabsorption of the substance by the proximal convoluted tubule is incomplete; consequently, part of the substance remains in the urine,o Thus renal threshold is the Drug concentration above which it appears in urine.