Which of the following are agranulocytes?

$A$: Blood group phenotype is controlled by the presence or absence of antigens present on the surface coating of $RBC$.
$R$: These antigens are of three types and are found in the oligosaccharide-rich head regions of a glycophorin.

Biological marriage of one of the following should be avoided:

Assertion: The regulation of $RBC$ production is accomplished by $FSH$.
Reason: Erythropoietin hormone circulates to red bone marrow where it increases stem cell mitosis and speeds up the development of $RBCs$.

The ion present in the highest concentration in blood plasma is........

A child of a mother with blood group $A$ and a father with blood group $AB$ may have any one of the following blood groups except