Inside the bulb:

Options

A. hydrogen is filled
B. air is filled
C. neon is filled
D. None of these

Answer

**Step-by-Step Solution:**

1. **Understanding the Bulb Structure**: An electric bulb consists of a glass enclosure that contains a tungsten filament. The filament is responsible for producing light when electricity passes through it.

2. **Identifying the Filament Material**: The filament is made of tungsten because it has a very high melting point. This is essential because the filament needs to withstand high temperatures without melting when electric current flows through it.

3. **Considering the Gas Inside the Bulb**: The question asks about the gas that is filled inside the bulb. The options provided are hydrogen, air, neon, and none of these.

4. **Analyzing the Options**:
- **Hydrogen**: Hydrogen is highly reactive and can explode at high temperatures, making it unsuitable for use inside a bulb.
- **Air**: Air contains oxygen, which can react with the hot tungsten filament, leading to oxidation and shortening the lifespan of the bulb.
- **Neon**: Neon is a noble gas, which means it is inert and does not react with other substances, even at high temperatures. This makes it a suitable choice for filling the bulb.

5. **Conclusion**: Given that neon gas is stable and does not react with the tungsten filament at high temperatures, the gas filled inside the bulb is **neon**.

**Final Answer**: The gas filled inside the bulb is **neon**.

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