In the ABO blood group system in humans, if a person of type-B blood has children with a person of type-AB blood, what blood types could their children have?

2 AB and 2BB

Explanation:

If a person type B blood group have children with AB blood type. There are 2 cases:

1- if BO cross with AB then children will be of AB, BB, AO, and BO.

2- if BB costs with AB then children will be of AB, BB, AB, and BB.

O is a recessive allele it only express when in OO form than a person has O blood group.