A Man and His Wife Are Having Trouble Having a Baby

Multiple Choice

A man and his wife are having trouble having a baby. Using modern technologies, the woman's eggs are removed, fertilized with her husband's sperm, and implanted into her uterus. The procedure is successful, and the woman gives birth to a healthy baby boy. After a while, though, they discover that their son is colorblind and has blood type O. The woman claims that the child can't be theirs since she has blood type A and her husband has type B. Also, neither parent is colorblind, although one grandparent (the woman's father) is also colorblind.
-As a genetic counselor, you would explain to the parents that

A) the eggs must have been accidentally switched, since the baby's blood type has to match one of his parents.
B) each parent could have contributed one recessive allele, resulting in type O blood.
C) the eggs must have been accidentally switched, since a type A parent and a type B parent can have any type children except O.
D) it is possible for the baby to have type O blood, since type O is inherited through a dominant allele.