The following is not an endothermic reactions:

Options

A. Combustion of methane
B. Decompositions of water
C. Dehydrogenation of ethane to ethylene
D. Conversion of graphite to diamond

Explanation

To determine which of the given reactions is not an endothermic reaction, we first need to understand the definitions of endothermic and exothermic reactions.

### Step-by-Step Solution:

1. **Understand Endothermic and Exothermic Reactions**:
- Endothermic reactions are those that absorb energy from their surroundings, usually in the form of heat, light, or electricity.
- Exothermic reactions are those that release energy to their surroundings.

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