Biology blood groups

answer is D
can someone explain? if the father has B and O and the mother has A and O, wouldn’t one of the children has OO?

Yes which answer did you put down?
I think type O can be considered as recessive in the sense that you would need the O allele from both parents to get Type O
As they can produce children with all four blood group types A, B, AB and O they’d both need to be heterozygous to be able to do this - ruling out the first 2 options
Option C - Type O blood cant be produced (Just A, B & AB)
So that leaves Option D