Why is it important to know a person's rhesus factor before a blood transfusion?

A person who is Rh– can develop antibodies if exposed to Rh+ blood, so Rh status matters when matching blood for a transfusion. Rh– patients should receive Rh– blood. Rh+ patients can generally receive either Rh+ or Rh– blood, so choices A and C are too restrictive.

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