What will be the blood group of ababy when father has b plus blood group and mother has o plus blood group?

The child can be A, B or AB. The only group the child shouldn't be is O.

You receive one allele from each parent. Each group actually has two places. Therefore the B is actually BO or BB.

If child is A, this means the mother's group is BO.

Now mix and match.

Mother gives B Father gives B Child is B

Mother O Father B Child B

Mother O Father A Child A

Mother B Father A Child AB

Mother B Father B Child B

The Rh factor is similar but not so easily determined. While it also has two places, the + can hold a - for it's second placement +-

For instance, my mother is AB Neg but all of her children are Pos. This means her Rh factor must be -+.

Hope this helps.