What is indicated by:
Blue flame of a bunsen burner?

Explanation

**Step-by-Step Solution:**

1. **Understanding the Bunsen Burner**: A Bunsen burner is a common laboratory device used for heating, sterilization, and combustion. It produces a flame when gas is ignited.

2. **Identifying the Flame Color**: When the Bunsen burner is lit, it can produce different flame colors depending on the combustion process. The two main flame colors are blue and yellow.

3. **Complete vs. Incomplete Combustion**:
- **Complete Combustion**: This occurs when there is enough oxygen for the fuel to react completely. In this case, hydrocarbons burn efficiently, producing carbon dioxide and water. The flame appears blue.
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