Correct Answer - d
Nephrons are the filtration units of kidneys. It is the structural and functional unit of a kidney and has three functions - filtration , reabsorption and secretion. Urine from the kidney passes through a tube called urter , that carry ureter, that carry urine into the urinary bladder. The urethra is a canal that carries urine from bladder and expels it out of body. Neurons are the nerve cells and are functional units of nervous system.