GFR {That is, clearance of "X" is greater than GFR.} It means, urinary excretion of the substance (Ux x V) is greater than the total filtration of the substance (Px x GFR). So the substance must have been secreted by the tubules. Option B is correct. If is greater than , it means the amount of total filtered substance is greater than its urinary excretion. In that case, the substance is being reabsorbed from the tubules. Option C: If a substance is being reabsorbed as well as secreted (for instance, K+), and if the amount of its secretion is greater than its reabsorption, there would be net secretion of the substance. And, its renal clearance would be greater than GFR. Hence, this option could have qualified as a correct statement. However, the amounts of its reabsorption and secretion are not mentioned in the option. Hence, option B should be taken as the most appropriate answer.">