The most popularly known blood group is the ABO grouping. It is named ABO and not ABC, because ‘o’ in it refers to having
A) No antigens A and B on RBC’s
B) Other antigens besides A and B on RBC’s
C) Over dominance of this type on the genes A and B types
D) One antibody only; either anti-A or anti-B on the RBC’s.

Hint:-The ABO grouping system was discovered by Karl Landsteiner in the year 1901. Today more than thirty blood groups are recognized. The most clinically relevant ones are the ABO blood group and grouping based on the Rhesus system. The blood group of an individual is determined by the presence or absence of antigens on the red blood cell.

Complete answer:-
As mentioned earlier it is the antigens that determine the blood group of an individual. There are four different groups.
Individuals with blood group A will have type A antigen present on the RBC. Individuals with blood group B will have type B antigen present on the RBC. Individuals with blood group AB will have both type A and type B antigens present on the RBC. No antigens are present on the RBC surface in case individuals with O blood group.
Other antigens apart from A and B do not play any role in ABO blood grouping.
A single gene manages the entire ABO blood group. There are three alleles present- i,,. The i gene is actually a recessive allele. If a person receives both i allele from his parents only then he will have O blood group. In all other cases, the other two alleles will dominate.
Presence of antigen on the RBC and not antibody determines a person’s blood group.


Therefore the correct option is (A).

Note:- People with blood group AB can receive blood from any other blood group. As antibodies (anti- A and Anti-B) are absent in their plasma. People with blood group O are called universal donors. The absence of antigens on the RBC does not elicit an immune response in the recipient.