A father is blood type B and a mother is blood type A. They have a child with blood type O. What are the genotypes of the father and mother?

A) The father must be BB and the mother must be AO.
B) The father must be BO and the mother must be AA.
C) The father must be BO and the mother must be AO.
D) The father must be BB and the mother must be AA.
E) This isn't possible.