Why Do Rh-Negative but Not Rh-Positive Mothers Sometimes Have Babies

Why do Rh-negative but not Rh-positive mothers sometimes have babies with hemolytic disease of the newborn?

A) This disease results when an Rh-negative mother's immune system is primed to produce anti-Rh IgG antibodies that can cross the placenta. If the mother is Rh-positive, she won't produce any anti-Rh antibodies at all.
B) Rh-positive mothers produce IgM antibody, not IgG. Even although they make anti-Rh antibody, IgM antibody can't cross the placenta, so it can't cause hemolytic disease of the newborn.
C) Rh-positive mothers will receive a preventative shot from their physician prior to conception. This will provide the protection the fetus needs AFTER conception to avoid the disease.
D) Rh-negativity is also associated with hyperproduction of antibodies. As such, Rh-negative mothers are more likely than Rh-positive mothers to produce the antibodies needed to produce this disease.
E) This disease results when an Rh-positive mother's immune system is primed to produce anti-Rh IgG antibodies that can cross the placenta. If the mother is Rh-negative, she won't produce any anti-Rh antibodies at all.