Antiserum used is testing blood groups has

Options

A. antibodies
B. antigens
C. leucocytes
D. RBCs

Explanation

**Step-by-Step Solution:**

1. **Understanding Blood Groups**: There are four main blood groups: A, B, AB, and O. Each blood group is determined by the presence or absence of specific antigens on the surface of red blood cells (RBCs).

2. **Identifying Antigens**:
- **A Blood Group**: Contains A antigens on the surface of RBCs.
- **B Blood Group**: Contains B antigens on the surface of RBCs.
- **AB Blood Group**: Contains both A and B antigens on the surface of RBCs.
- **O Blood Group**: Contains no antigens on the surface of RBCs.

3. **Role of Antiserum**: Antiserum is used in blood typing and contains antibodies that react with specific antigens. The interaction between antibodies in the antiserum and the antigens on the RBCs determines the blood group.

4. **Testing Procedure**:
- When testing a blood sample, specific antisera are added:
- **Anti-A Serum**: Contains antibodies against A antigens.
- **Anti-B Serum**: Contains antibodies against B antigens.
- If the blood sample is type A, it will coagulate when mixed with anti-A serum due to the presence of A antigens.
- If the blood sample is type B, it will coagulate when mixed with anti-B serum due to the presence of B antigens.
- If both antisera cause coagulation, the blood type is AB (both A and B antigens are present).
- If there is no coagulation with either antiserum, the blood type is O (no antigens present).

5. **Conclusion**: The antiserum used in testing blood groups contains antibodies. Therefore, the correct answer to the question is that the antiserum has antibodies.

**Final Answer**: Antiserum used in testing blood groups has antibodies.

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