Incompatibility in the Rh blood system can result in hemolytic disease of the newborn.Which combination poses the greatest risk?

A) Rh positive mother, Rh negative fetus
B) Rh positive father, Rh negative fetus
C) Rh negative mother, Rh positive fetus
D) Rh negative mother, Rh negative fetus
E) Rh positive mother, Rh negative father