In erythroblastosis foetalis,which factors of the mother pass through the placenta into the foetus?

The ratio of $RBC$ to $WBC$ in man is (in $: 1$)

$A$ person having blood group $O$ can receive blood of:

The liver does not synthesize which of the following proteins?

Identify the cells and their functions based on the provided figure:
$(a)$ Fig. $A$ - Megakaryocyte - formation of platelets
$(b)$ Fig. $B$ - Lymphocyte - synthesis of antibodies
$(c)$ Fig. $A$ - Eosinophil - secrete antihistamine
$(d)$ Fig. $A$ - Neutrophil - secrete heparin

What is the principal cation in human blood?