Which of the following statements is true?

without kidneys, the body cannot remove liquid waste from the blood.
the excretory system is made of all the hormone-secreting glands in the body.
the immune system is made of red and white blood cells.
white blood cells are part of the cardiovascular system.

Without kidneys, the body cannot remove liquid waste from the blood.

Explanation:

Humans have two kidneys, which are dark red, bean-shaped glands located in the posterior abdomen, behind the peritoneum and beside the spine in the lower back. They are part of the excretory and osmoregulatory system because they filter and excrete the waste in the blood.

Microscopically, it is made up of about 1 million small structures called nephron. Each nephron eliminates blood waste, maintains the body's electrolyte balance, controls the amount of fluid in the body, regulates blood pressure and secretes hormones, and produces urine. Therefore, the nephron is called the kidney functional unit, as each nephron performs all renal functions.