In humans,multiple alleles are seen controlling the inheritance of which of the following?

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

The number of phenotypes in $ABO$ blood group is

The plasma membrane of the red blood cells has ...$A$... polymers that protrude from its surface and the kind of sugar is controlled by the gene. The gene $I$ has three alleles ...$B$... The alleles and produce a slightly different form of the sugars,while allele $i$ doesn't produce any ...$C$...
Choose the correct option for $A, B$ and $C$.

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:
$A. I^Bi / I^Ai / ii$
$B. I^BI^B / I^AI^A / ii$
$C. I^AI^B / iI^A / I^Bi$
$D. I^Ai / I^Bi / I^Ai$
$E. iI^B / iI^A / I^AI^B$

In humans,how many genotypes and phenotypes are produced by the three different alleles of the $ABO$ blood group system?