Detection of blood groups is done by agglutination test using antiserum. According to this method, if the blood shows coagulation with

Options

A. (a) antiserum B, blood group is AB
B. (b) antiserum B, blood group B
C. (c) antiserum A and B, blood group is O
D. (d) antiserum A, blood group is O

Answer

To determine the blood group using the agglutination test with antiserum, follow these steps:

### Step-by-Step Solution:

1. **Understanding Blood Groups**: Blood groups are determined by the presence of specific antigens on the surface of red blood cells (RBCs). The main blood groups are A, B, AB, and O, which correspond to the presence or absence of A and B antigens.

2. **Role of Antiserum**: Antiserum contains antibodies that react with specific antigens. For example, antiserum A contains antibodies against A antigens, and antiserum B contains antibodies against B antigens.

3. **Testing with Antiserum**: When a blood sample is mixed with antiserum, agglutination (clumping) occurs if the corresponding antigen is present. For instance:
- If blood is mixed with antiserum A and agglutination occurs, the blood group is A (presence of A antigen).
- If blood is mixed with antiserum B and agglutination occurs, the blood group is B (presence of B antigen).
- If blood is mixed with both antisera A and B and agglutination occurs, the blood group is AB (presence of both antigens).
- If there is no agglutination with either antiserum, the blood group is O (absence of both antigens).

4. **Analyzing the Given Options**: The question presents four options regarding the reaction of blood with different antisera:
- **Option A**: Antiserum B - Blood group AB
- **Option B**: Antiserum B - Blood group B
- **Option C**: Antiserum A and B - Blood group O
- **Option D**: Antiserum A - Blood group O

5. **Determining the Correct Answer**:
- If the blood shows coagulation with **antiserum B**, it indicates the presence of B antigen on the RBCs. Therefore, the blood group must be **B**.

6. **Final Conclusion**: The correct answer is **Option B**: If the blood shows coagulation with antiserum B, then the blood group is B.