Answer: Blood
Explanation:
Kidney is body organ that is placed in vertebrates of the renal system of the humans.It is two units with bean -like shape.The major function that kidneys performs in the body is extracts and flush out the waste and fluid from the body in the form urine.
Before the blood reaches to the heart, kidneys also perform the function of filtering blood.This helps the body to remain healthy as all the waste gets eliminated from he blood and body.
