The protein that is a structural material is

Options

A. Albumin
B. Oxytocin
C. Haemoglobin
D. Keratin

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for a specific protein that serves as a structural material in biological systems.

2. **Identifying the Options**: The options provided are:
- Albumin
- Oxytocin
- Hemoglobin
- Keratin

3. **Analyzing Each Option**:
- **Albumin**: This is a globular protein primarily found in blood plasma and is involved in maintaining osmotic pressure, not a structural protein.
- **Oxytocin**: This is a peptide hormone involved in childbirth and lactation, not a structural protein.
- **Hemoglobin**: This is a globular protein that carries oxygen in the blood, also not a structural protein.
- **Keratin**: This is a fibrous protein that forms the structural material in hair, nails, feathers, and horns.

4. **Conclusion**: Among the options, keratin is the only protein that serves as a structural material. It is known for its role in providing strength and protection in various biological structures.

5. **Final Answer**: The protein that is a structural material is **Keratin**.