In the ABO system, blood group ‘O’ is characterized by the:

The correct option is absence of both antigen A and antigen B.

Explanation:
The ABO blood group system is classified based on the presence or absence of specific inherited antigen molecules on the surface of red blood cells (erythrocytes). These antigens are designated as Antigen A and Antigen B.

Depending on the combination of these antigens, there are four main blood groups:
1. Blood Group A: Red blood cells have Antigen A on their surface.
2. Blood Group B: Red blood cells have Antigen B on their surface.
3. Blood Group AB: Red blood cells have both Antigen A and Antigen B on their surface.
4. Blood Group O: Red blood cells have neither Antigen A nor Antigen B on their surface.

Because individuals with blood group 'O' lack both A and B antigens on the surface of their red blood cells, this blood type is characterized by the absence of both antigen A and antigen B.