Mannitol is stored food of

Options

A. Rhodophyceae
B. Xanthophyceae
C. Chlorophyceae
D. Phaeophyceae.

Answer

**Step-by-Step Solution:**

1. **Identify the Groups:** The question asks about the stored food of different algal groups: Rhodophyceae, Xanthophyceae, Chlorophyceae, and Phacophyceae.

2. **Analyze Rhodophyceae:** This group is known as red algae. The stored food in Rhodophyceae is in the form of Floridian starch.

3. **Analyze Xanthophyceae:** This group is known as yellow-green algae. The stored food in Xanthophyceae is glycogen.

4. **Analyze Chlorophyceae:** This group is known as green algae. The stored food in Chlorophyceae is typically in the form of starch and oil.

5. **Analyze Phacophyceae:** This group is known as brown algae. The stored food in Phacophyceae includes mannitol, along with other substances like laminarin and oil.

6. **Conclusion:** Based on the analysis, mannitol is specifically identified as the stored food of Phacophyceae.

7. **Final Answer:** Therefore, the correct answer to the question is option D: Phacophyceae.

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