Answer:
D. They release waste into the bloodstream.
Step-by-step explanation:
Kidneys are the primary organs of the excretory system. Their primary function is to remove the metabolic waste from the blood and release it out of the body in the form of urine. The nitrogenous waste, drugs, uric acid, and other metabolic waste products are removed from blood in kidneys.
Hence, kidneys do not release the waste into the bloodstream, rather release them out of the body and filter the blood.