Epitope lies on antigen/antibody.

Explanation

**Step-by-Step Solution:**

1. **Understanding Antigens and Antibodies:**
- An antigen is a foreign molecule that can induce an immune response in the body. It is typically a part of pathogens like bacteria, viruses, or other foreign substances.
- An antibody, on the other hand, is an immunoglobulin produced by the immune system in response to an antigen. It specifically targets and binds to the antigen.

2. **Role of Epitopes:**
- Epitopes are specific regions or structures on the antigen that are recognized by the immune system. They are the precise sites where antibodies bind.
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