Common example of red algae is

Options

A. porphyra
B. Batrachosperum
C. ectocarpus
D. both a and b

Explanation

**Step-by-Step Solution:**

1. **Identify the Question**: The question asks for a common example of red algae.

2. **Review the Options**: The options provided are:
- A) Porphyra
- B) Petrachospermum
- C) Ectocarpus
- D) Both A and B

3. **Analyze Option A - Porphyra**:
- Porphyra is a species of red algae that belongs to the category Rhodophyceae.
- It is typically found in shallow seawater, making it a marine algal species.
- There are approximately 70 species under the genus Porphyra.

4. **Analyze Option B - Petrachospermum**:
- Petrachospermum is also a species of red algae.
- Unlike Porphyra, it is a freshwater algal species, usually found near the banks of lakes and rivers, particularly in slow-running water.

5. **Analyze Option C - Ectocarpus**:
- Ectocarpus is not a red algae; it is classified as brown algae.
- It has a filamentous body structure, which distinguishes it from red algae.

6. **Analyze Option D - Both A and B**:
- Since both Porphyra (marine) and Petrachospermum (freshwater) are examples of red algae, this option is also valid.

7. **Conclusion**: The correct answer is that both A (Porphyra) and B (Petrachospermum) are common examples of red algae. Therefore, the best choice is option D.

**Final Answer**: Both A and B (Porphyra and Petrachospermum) are common examples of red algae.

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