Name one fuel which burns without producing a flame.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for a fuel that burns without producing a flame. This means we need to identify a type of fuel that, when it undergoes combustion, does not create a visible flame.

2. **Identifying Characteristics of Fuels**: Generally, fuels that produce flames are those that vaporize during combustion. When a fuel vaporizes, it forms flammable gases that ignite and create a flame.

3. **Considering Fuels that Burn without Flame**: To find a fuel that burns without producing a flame, we need to think of solid fuels that do not vaporize significantly when they burn.

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