Answer:
Option D, kidney
Explanation:
Renal failure is the severe impairment or total lack of kidney function, as reflected in the first word of the medical term.
The combining form ren/o- refers to the kidneys, originating from the Latin translation ren (plural renes).
Liver failure is usually referred to as such, same with heart failure. Bladder failure could refer to an incontinence or a neurogenic origin.
Renal failure is impaired function of the kidney(s), option D.
