………… From red alga is used in the preparation of chocolate .

Answer

**Step-by-Step Solution:**

1. **Identify the Source**: The question asks about a substance derived from red algae that is used in chocolate preparation. Red algae belong to the class Rhodophyceae.

2. **Name the Substance**: The specific substance obtained from red algae that is used in chocolate is called carrageenan.

3. **Understand the Composition**: Carrageenan is made up of D-galactose units. This is important as it highlights the chemical structure of the substance.

4. **Function of Carrageenan**: In the context of chocolate, carrageenan acts as a stabilizing and gelling agent. This means it helps to maintain the texture and consistency of the chocolate.

5. **Geographical Source**: Carrageenan is primarily extracted from red algae found in the North Atlantic region, which is significant for its availability.

6. **Conclusion**: Therefore, the answer to the question is that carrageenan from red algae is used in the preparation of chocolate.

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