Select the correct match from the following :
I. Humoral mediated immunity : Given by killer T - cells
II. – Anamnestic immune response : slow immune response.
III . Antigen binding site : variable region of both heavy and light chain .

Options

A. I,II,III
B. I and III
C. II and III
D. only III

Answer

To solve the question, we will analyze each statement one by one to determine which matches correctly.

### Step 1: Analyze Statement I
**Statement I:** Humoral mediated immunity: Given by killer T-cells.

- **Explanation:** Humoral immunity is primarily mediated by B-cells, which produce antibodies. Killer T-cells (also known as cytotoxic T-cells) are involved in cell-mediated immunity, not humoral immunity. Therefore, this statement is incorrect.

### Step 2: Analyze Statement II
**Statement II:** Anamnestic immune response: slow immune response.

- **Explanation:** The anamnestic response, also known as the secondary immune response, occurs when the immune system encounters an antigen it has previously encountered. This response is typically faster and stronger than the primary response due to the presence of memory cells. Thus, this statement is also incorrect.

### Step 3: Analyze Statement III
**Statement III:** Antigen binding site: variable region of both heavy and light chain.

- **Explanation:** The antigen binding site of an antibody is indeed located in the variable regions of both the heavy and light chains. This allows the antibody to bind specifically to different antigens. Therefore, this statement is correct.

### Conclusion
After analyzing all three statements, we find that only Statement III is correct. Thus, the correct match is:

**Correct Answer:** III. Antigen binding site: variable region of both heavy and light chain.

### Final Answer
The correct option is option number 4, which states that only Statement III is correct.

---