Placenta filters fetal waste during pregnancy

Steps:

• Identify the fetus's excretory products, like urea and carbon dioxide, produced via metabolism.
• Recall that these wastes exit the fetus through the umbilical cord into the placenta.
• Note the placenta's role in exchanging substances between fetal and maternal blood without mixing.
• Determine the labelled structure matching this exchange site as the waste remover.

Why C is correct:

• The placenta acts as the interface where fetal wastes diffuse into maternal blood for kidney excretion, per fetal circulation physiology.

Why the others are wrong:

• A: Uterus supports pregnancy but does not filter wastes.
• B: Amniotic sac provides cushioning and fluid, not waste removal.
• D: Umbilical cord transports blood but does not process wastes itself.

Final answer: C