Question

Could a man with O blood be the father of a child who has AB blood?

Answer 1

i think not because blood type o is rare

Answer 2

The child gets one chromosome from each parent. If the child is AB, it must have got an A from one of its parents and a B from the other. But if the father had an A or a B, he must have been either an A or a B (or an AB) himself. So no, in this case he can't be the child's father.