Question

Mary has type A blood and her husband (John) has type B blood. John's parents both had type AB. Mary and John havethree children, one with type A, one with type AB, and one with type B. Relatives suspect that one of the children was adopted.

Answer 1

Yeah, they are right!! Child with group A must be adopted

As john's genotype would be Ib Ib, which must pass his one Ib, and in the presence of that, offspring can't be of type A