If dad had a blood type of O and mom had a blood type of AB, could they have a child with B type blood?if so what percentage

Yes, they could give a child b type Blood.

Explanation:

Parents with blood types AB and O can give their children either A or B blood types, it's a 50% and 50%.

the answer would be d

a unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring.