Use the Following Information to Answer the Questions Below

Use the following information to answer the questions below.
A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N.
-If both children are of blood group MM, which of the following is possible?

A) Each parent is either M or MN.
B) Each parent must be type M.
C) Both children are heterozygous for this gene.
D) Neither parent can have the N allele.
E) The MN blood group is recessive to the ABO blood group.