Inheritance of $ABO$ blood group system is an example of

If a man with blood group $A$ marries a woman with blood group $AB$, and their first child has blood group $B$, what is the genotype of the child?

In a marriage between a male with blood group $A$ and a female with blood group $B$,the progeny had either blood group $AB$ or $B$. What could be the possible genotype of parents?

Alleles are

$A$ man with blood group $A$ marries a woman with blood group $AB$. Which type of offspring would indicate that the man is heterozygous for blood group $A$?

Blood group $B$ will have which of the following genotypes?