Rh Factor and It's Inheritance

Q. If the father of a fetus is Rh positive and the mother is Rh negative, what are the chances that there will be a mother-fetus incompatibility problem? Assume that the couple already had a first child with no medical problems.

1. 100%
2. At least 50%
3. Less than 50%
4. 0%

Q. A pregnant woman was asked to take an injection to check abortion which is due to Incompatibility of the embryo’s blood group .Why is it so? Name the condition