The type of combustion in which a material bursts suddenly into flame only own without application of any apparent cause, is called _____ combustion.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the type of combustion that occurs suddenly without any external heat source or apparent cause.

2. **Identifying the Term**: The term we are looking for is a specific type of combustion that happens spontaneously.

3. **Defining Spontaneous Combustion**: Spontaneous combustion is defined as the phenomenon where a material ignites and bursts into flames on its own, without any external heat source.

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