Which blood group lacks antigen on their RBCs ?

Options

A. O
B. A
C. B
D. AB

Answer

To determine which blood group lacks antigens on their red blood cells (RBCs), we can follow these steps:

### Step-by-Step Solution:

1. **Understand Blood Groups**: There are four main blood groups in the ABO system: A, B, AB, and O. Each blood group is defined by the presence or absence of specific antigens on the surface of red blood cells.

2. **Identify Antigens**:
- **Blood Group A**: Has antigen A on the surface of RBCs.
- **Blood Group B**: Has antigen B on the surface of RBCs.
- **Blood Group AB**: Has both antigen A and antigen B on the surface of RBCs.
- **Blood Group O**: Lacks both antigen A and antigen B on the surface of RBCs.

3. **Conclusion**: Since blood group O does not have any antigens (A or B) present on its RBCs, it is the only blood group that lacks antigens.

4. **Final Answer**: The blood group that lacks antigens on their RBCs is **O**.