Question

A woman gives birth to a son who has type A blood. She has type AB blood. Which of the following can be concluded from this about her parents' blood types?

- One of her parents had at least one A allele and the other at least one B allele.

- One of her parents had type AB blood.

- One of her parents had type B blood and the other type A blood

Answer 1

If there are two AB parents their child could have any of an A, B or AB, but not O blood type.
If there are two A parents their child could have either A or O children, but not B nor AB.
Look at it like this:
AB = one A and one B
B = two B's or one B and one O
A = two A's or one A and one O
O = two O's
Since the parent is AB the parents will pass on an A or B.
So using the information I gave you you can eliminate some choices.
We already know the mother is AB. So it is a must that her father had type AB or A or even O blood.
Understand?

Answer 2

So from what you're telling me, the answer choice is C.

Answer 3

Yeah.