Blood composition in renal artery vs. vein

Steps:

• Vessel X is the renal artery, carrying blood from the aorta to the kidney.
• Vessel Y is the renal vein, returning filtered blood from the kidney to the inferior vena cava.
• The renal artery contains higher urea levels from systemic circulation, while the kidney filters urea into urine, lowering it in the renal vein.
• The renal artery has higher oxygen for kidney metabolism, which consumes oxygen, reducing it in the renal vein.

Why B is correct:

• Statements 1 and 3 align with renal filtration removing urea (definition: kidneys excrete waste via nephrons) and oxygen use by kidney tissue.

Why the others are wrong:

• A includes false statement 2, as renal vein has less oxygen than artery.
• C omits true statement 3 about higher oxygen in artery.
• D excludes true statement 1 and includes false statement 2.

Final answer: B