Blood cells -

Analogy type questions:
$(1)$ Human $RBCs$ : Enucleated : : $WBCs$ : ......
$(2)$ $'O'$ blood group : Universal donor : : $'AB'$ blood group : ......

Four children belonging to the same parents have the following blood groups $A$,$B$,$AB$ and $O$. Hence,the genotypes of the two parents are:

Which of the following are the macrophages of the spleen?

Which of the following white blood cells are present in the maximum number?

In a medico-legal case of accidental interchange between two babies in a hospital,the baby with blood group $A$ could not be the child of parents with which of the following blood group combinations?