<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:An investigator is attempting to assess the glomerular filtration rate GFR of a healthy adult volunteer. The volunteers inulin clearance is evaluated under continuous inulin infusion and urine collection and compared to the creatinine clearance. It is found that the estimated GFR based on the volunteers creatinine clearance is 129 mLmin and the estimated GFR calculated using the inulin clearance is 122 mLmin. Which of the following is the best explanation for the difference in these measurements?? A: Creatinine is not freely filtered, B: Inulin is actively secreted, C: Inulin is not freely filtered, D: Creatinine is passively reabsorbed, E: Creatinine is actively secreted,  <response>: This is a question asking about the differences between measuring GFR using inulin clearance versus creatinine clearance. Inulin is an ideal filtration marker that is freely filtered at the glomerulus without being reabsorbed or secreted by the tubules. Therefore, inulin clearance provides an accurate measure of GFR. Creatinine is filtered at the glomerulus, but it is also secreted by the proximal tubule. This secretion of creatinine leads to an overestimation of GFR when it is measured by creatinine clearance.The choices provide different explanations for why the creatinine clearance estimate of GFR is higher than the inulin clearance estimate. Based on the information provided, the explanation is that creatinine is actively secreted by the tubules, leading to an overestimation of GFR by creatinine clearance.E: Creatinine is actively secreted 