A man of blood group A marries a woman of blood group of AB ,which type of progeny would indicate that man is heterozygous?

Hello Student
If the progeny is of B blood group; this indicates that the man is heterozygous.
If the male parent is homozygous for A, then only possibility of Progeny is with blood group A or AB.
Or if male parent is heterozygous A; then the possibility of progeny is A, B or AB blood group.

You can make number of crosses as explained here with different blood grouping of father and mother.