For protecting a magnetic needle it should be placed:

Options

A. In iron box
B. In wooden box
C. In metallic box
D. None of these

Explanation

To determine how to protect a magnetic needle from external magnetic fields, we can analyze the options given:

1. **Understanding the Problem**: The magnetic needle is sensitive to external magnetic fields, which can cause it to become magnetized. The goal is to find a way to shield the needle from these external influences.

2. **Evaluating the Options**:
- **Iron Box**: Iron is a ferromagnetic material, meaning it can become magnetized. When a magnetic needle is placed inside an iron box, the iron will magnetize itself in response to the external magnetic field. This self-magnetization creates a magnetic field that opposes the external field, effectively shielding the needle inside from being affected.
- **Wooden Box**: Wood is not a magnetic material and does not provide any magnetic shielding. Therefore, placing the needle in a wooden box would not protect it from external magnetic fields.
- **Metallic Box**: Depending on the type of metal, a metallic box may not provide effective shielding. Non-ferromagnetic metals (like aluminum) do not have the same magnetic properties as iron and would not protect the needle as effectively.

3. **Conclusion**: The best option for protecting the magnetic needle is to place it in an **iron box**. The iron will magnetize itself and create a protective barrier against external magnetic fields.

Final Answer: The magnetic needle should be placed in an **iron box**.

---