Which of the following accurately describes kidney function?
a. kidneys will excrete salts if you have too little in your blood.
b. kidneys are directed by the presence of antidiuretic hormone to excrete more water in urine.
c. kidney function is controlled by the blood's composition and hormones.
d. kidneys can excrete salts, but not glucose.

The main purpose of the Kidneys are fluid balance, clearing waste, regulating blood pressure, making certain hormones, and balancing chemicals in the blood. So A would be wrong they do not excrete salts. B is wrong due to the fact antidiuretics reduce urination. C. is correct, blood composition and hormones tell the kidneys what needs to be done, such like if your blood pressure get to high the kidenys will react by releasing hormones in the blood to reduce sodium and increase urination. D. Sodium is reabsorted by the kidneys not excreted. And Glucose shouldn't be in urine it usally reabsorbed at a 100% unless you have diabetes mellitus. So part of D is correct.

An egg, or a sack of flour