Which of the following is an excellent example of multiple alleles?

$A$ man with blood group $AB$ marries a woman with $O$ blood group. In this situation,

If a child has $O$ type of blood group and the father has $B$ type,the genotype of the father will be:

The offspring produced from a marriage have only $O$ or $A$ blood groups. Of the genotypes given below,the possible genotypes of the parents would be

As per the $ABO$ blood grouping system,the blood group of the father is $B^{+}$,the mother is $A^{+}$,and the child is $O^{+}$. Their respective genotypes can be:
Choose the most appropriate answer from the options given below:
$A. I^Bi / I^Ai / ii$
$B. I^BI^B / I^AI^A / ii$
$C. I^AI^B / iI^A / I^Bi$
$D. I^Ai / I^Bi / I^Ai$
$E. iI^B / iI^A / I^AI^B$

If a man with blood group $A$ marries a woman with blood group $AB$,which of the following offspring would indicate that the man is heterozygous for blood group $A$?