Which of these fibres smells like burning hair on heating?

Options

A. Acrylic
B. Cotton
C. Rayon
D. Silk

Explanation

**Step-by-Step Solution:**

1. **Identify the Question**: The question asks which fiber smells like burning hair when heated.

2. **Understand the Options**: The question likely provides multiple options, but we need to focus on the characteristics of the fibers mentioned.

3. **Recognize Natural Fibers**: Among the fibers, we need to identify which ones are natural. Natural fibers are typically derived from plants or animals.

4. **Consider the Smell of Burning Hair**: Burning hair has a distinct smell due to its protein composition. Therefore, we need to find a fiber that is also protein-based.

5. **Identify the Fiber**: Silk is a natural fiber obtained from silkworms. Since silk is a protein fiber, it will emit a smell similar to that of burning hair when heated.

6. **Conclusion**: Based on the analysis, the fiber that smells like burning hair on heating is silk.

**Final Answer**: Silk (Option number 4).

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