What is a role of the kidney in the excretory system of mammals?
(A)To remove salt from the body and to keep water in the body
(B)To remove water from the body and to keep salt in the body
(C)To remove nitrogenous waste from the body and to maintain water levels in the body
(D)To remove water from the body and to maintain levels of nitrogenous substances in the body
Answer: C