To Measure GFR, an Individual's Urine Is Examined for the Concentration

Multiple Choice

To measure GFR, an individual's urine is examined for the concentration of a test substance that they received by injection. How is that test substance treated by the kidney?

A) It is filtered, reabsorbed, and excreted, but it is not secreted.
B) It is neither filtered nor reabsorbed, but it is secreted.
C) It is filtered but neither reabsorbed nor secreted.
D) It is filtered and secreted, but not reabsorbed.
E) It is not filtered, but it is secreted and reabsorbed.