Question

Humans have yet another antigen system on their red blood cells. The MN blood group refers to a different antigen controlled by codominant alleles (MM, MN, and NN). A woman with blood types (O, MN, Rh+) had a baby with a man with the blood types (AB, N, Rh-). Unfortunately there was a mix up at the hospital, which of the following children belongs to the couple? And why?

a. Child #1: AB, N, Rh+
b. Child #2: A, M, Rh+
c. Child #3: A, MN, Rh-
d. Child #4: B, M, Rh+
e. Child #5: O, MN, Rh+
f. Child #6: O, MN, Rh-

I think it's child B or D but I'm not sure...