A man of unknown genotype has type B blood, his wife has type A blood (also unknown genotype). List ALL the blood types possible for their children. (you may need to do multiple crosses to consider the different possible genotypes of the parents)

AB, aB, Ab

Explanation:

Man has blood type B so could be BB (homozygous dominant) or could be Bb (heterozygous)

Woman has blood type A, so she could be AA (heterozygous dominant) or Aa (heterozygous)

Now, we need to make a separate cross for woman with AA, man with BB and we get children of all AB

Then we can make another cross for genotypes Aa and BB, and we get AB and aB

We can continue this for AA, Bb and for Aa, Bb