Look at figure 30–2. filtered blood leaves the kidney and returns to circulation through the
a. renal artery.
b. renal vein.
c. urinary bladder.
d. urethra.

The answer is A. renal vein. 

Renal veins drain the kidneys and carry the blood filtered by kidneys. Renal artery cannot be the right choice because it carries blood to the kidneys. Urinary bladder collects urine from the kidneys. Urethra connects urinary bladder to the external urethral orifice. Therefore, the only correct choice is renal vein (A).

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