Which of the following statements is incorrect?

Options

A. A person of 'o' blood group has anti 'A' and anti 'B' antibodies in his blood plasma
B. A person of 'B' blood group can't donate blood to a person of 'A' blood group
C. Blood group is designated on the basis of the presence of antibodies in the blood plasma
D. A person of AB blood group is universal recipient.

Answer

To determine which statement is incorrect regarding blood groups, we will analyze each statement one by one based on our understanding of blood group classification, antibodies, and antigens.

### Step-by-Step Solution:

1. **Understanding Blood Groups and Antibodies**:
- Blood groups are classified based on the presence of specific antigens on the surface of red blood cells (RBCs).
- The main blood groups are A, B, AB, and O.
- Each blood group has corresponding antibodies in the plasma:
- **Group A**: Has A antigens on RBCs and anti-B antibodies in plasma.
- **Group B**: Has B antigens on RBCs and anti-A antibodies in plasma.
- **Group AB**: Has both A and B antigens on RBCs and no antibodies in plasma.
- **Group O**: Has no antigens on RBCs and both anti-A and anti-B antibodies in plasma.

2. **Analyzing the Statements**:
- **Statement 1**: "A person of O blood group has anti A and anti B antibodies in blood plasma."
- This statement is **true** because O blood group individuals do have both anti-A and anti-B antibodies.

- **Statement 2**: "A person of B blood group cannot donate blood to the A blood group."
- This statement is **true** because B blood group has anti-A antibodies, which would react with A antigens present in A blood group.

- **Statement 3**: "Blood group is designated on the basis of presence of antibodies in the blood plasma."
- This statement is **incorrect**. Blood groups are designated based on the presence of antigens on the surface of RBCs, not antibodies in the plasma. Therefore, this is the wrong statement.

- **Statement 4**: "A person with AB blood group is a universal recipient."
- This statement is **true** because AB blood group individuals can receive blood from any blood type (A, B, AB, or O) without any adverse reactions.

3. **Conclusion**:
- The incorrect statement is **Statement 3**: "Blood group is designated on the basis of presence of antibodies in the blood plasma."

### Final Answer:
The incorrect statement is: **"Blood group is designated on the basis of presence of antibodies in the blood plasma."**