An Rh-positive mother should be concerned about erythroblastosis fetalis under which circumstance?

A) If the father is Rh-negative,the Rh-positive mother should be concerned.
B) If this is her second child and she has not taken RhoGAM,Rh-positive mother should be concerned.
C) She should not be at all concerned about erythroblastosis fetalis.
D) Both A and B are correct.