The proteins found in the filaments of muscle fibres are

Options

A. actin and myosin
B. myosin and elastin
C. actin only
D. myelin and tubulin

Explanation

To answer the question regarding the proteins found in the filaments of muscle fibers, we can follow these steps:

### Step-by-Step Solution:

1. **Identify Muscle Fiber Structure**: Muscle fibers are made up of myofilaments, which are the basic units of muscle contraction.

2. **Differentiate Between Myofilaments**: There are two types of myofilaments in muscle fibers:
- **Thick Myofilaments**: These are primarily composed of the protein **myosin**.
- **Thin Myofilaments**: These are primarily composed of the protein **actin**.

3. **List the Proteins**: The two main proteins found in the filaments of muscle fibers are:
- **Actin** (found in thin myofilaments)
- **Myosin** (found in thick myofilaments)

4. **Evaluate the Options**:
- **Option A**: Actin and Myosin - This is correct as both are present in muscle fibers.
- **Option B**: Myosin and Elastin - Incorrect, as elastin is not found in muscle fibers but in connective tissues.
- **Option C**: Actin only - Incorrect, as myosin is also present.
- **Option D**: Myelin and Tubulin - Incorrect, as myelin is related to nerve fibers and tubulin is part of the cytoskeleton.

5. **Conclusion**: The correct answer to the question is that the proteins found in the filaments of muscle fibers are **Actin and Myosin**.