Question

why is it important to know a persons rhesus factor before a blood transfusion?
a patient who is rh+ can receive only rh- blood.
a patient who is rh- can receive only rh+ blood.
a patient who is rh+ can receive only rh+ blood.
a patient who is rh- can receive only rh- blood.

Explanation:

When a person with Rh - blood (Rh−) receives Rh+ blood, their immune system will produce antibodies against the Rh factor. If they receive Rh+ blood again in the future, it can cause a serious transfusion reaction. So, an Rh− patient should receive only Rh− blood.

Answer:

A patient who is Rh− can receive only Rh− blood.