The problem due to Rh^- factor arises when the blood of two (Rh⁺ and Rh^-) mix up
(a) During pregnancy
(b) Through transfusion
(c) In a test tube
(d) Both A and B

Hint:If an Rh-negative person is exposed to the Rh-positive blood, specific antibodies will be formed in the body of the person against the opposite Rh antigens. The Rh factor of the blood matters in both the conditions, i.e. during pregnancy and during the blood transfusion.

Complete answer: Rh antigens are found on the surface of RBCs and nearly 80% if the individuals have it and so they are Rh-positive or Rh+. The rest 20% are Rh-negative or Rh^-.
During a blood transfusion, if an Rh-negative person is given Rh-positive blood, the antibodies will be formed against the Rh-positive antigens which will cause serious health conditions for the recipient. Similarly, during pregnancy, if the mother and fetus have different Rh factors, the condition is termed as Rh incompatibility and there are chances of hemolytic disease of the fetus and newborn.

It occurs specifically during pregnancy when the mother is Rh-negative and her baby is Rh-positive and some of the fetus Rh-positive RBCs get into the mother’s bloodstream. Generally, the anti-D antibody is not found in the plasma of Rh+ or Rh- blood but when exposed to other types, antibodies are formed by the immune cells.

So, the correct answer is ‘Both A and B’.

Note:The Rh antigen is also called D antigen and in the RBC blood group system, there are more than 50 different Rh antigens.
1. The Rh antigens are highly immunogenic and most of the time these antigens are responsible for causing hemolytic transfusion reactions.
2. After A and B antigens, the D antigens are the most important blood cell antigens in the transfusion practices.