A person with antigens A and B and no antibodies belongs to blood group or in which blood group antibodies are absent

The correct answer is AB.

To understand why a person with both antigens A and B and no antibodies belongs to blood group AB, we can look at the ABO blood group system, which is determined by the presence or absence of specific antigens on the surface of red blood cells (RBCs) and the corresponding antibodies in the blood plasma.

1. Antigens: These are sugar molecules (glycoproteins) located on the outer membrane of red blood cells. The two main antigens in this system are Antigen A and Antigen B.
2. Antibodies: These are immune system proteins found in the plasma. They recognize and bind to foreign antigens to protect the body. In the ABO system, an individual naturally produces antibodies against whichever antigen (A or B) is not present on their own red blood cells. This prevents the body's immune system from attacking its own blood cells.

Let's examine how this determines the four main blood groups:
- Blood Group A: Red blood cells have antigen A on their surface. The plasma contains anti-B antibodies.
- Blood Group B: Red blood cells have antigen B on their surface. The plasma contains anti-A antibodies.
- Blood Group AB: Red blood cells have both antigen A and antigen B on their surface. Because both antigens are present as "self" markers, the body does not produce any antibodies against them. Therefore, antibodies are absent in the plasma of blood group AB.
- Blood Group O: Red blood cells have neither antigen A nor antigen B on their surface. The plasma contains both anti-A and anti-B antibodies.

Since the question describes an individual who possesses both antigens A and B on their red blood cells and has no antibodies in their plasma, they belong to blood group AB.