On what is the $ABO$ blood grouping based?

The $pH$ of human blood is:

Which of the following is true for blood group '$O$'?

What are the cellular components of blood?

What is the percentage of $Hb$ (hemoglobin) in $RBC$ (red blood cells) (in $\%$)?

Select the incorrect statements with reference to $Rh$ grouping.
$A$. Erythroblastosis foetalis is a condition observed having foetus with $Rh^{+ve}$ blood and mother with $Rh^{+ve}$ blood.
$B$. $Rh$ antigen is observed on $RBCs$ in the majority of human beings.
$C$. Before blood transfusion, $Rh$ group should also be matched.
$D$. $Rh$ incompatibility is observed when a pregnant mother is $Rh^{-ve}$ and the foetus is $Rh^{+ve}$.
$E$. Erythroblastosis foetalis can be avoided by administering anti-$Rh$ antibodies to the mother immediately after the delivery of the second child.
Choose the answer from the options given below: