Which of the following is a red alga that is not red?

Options

A. Nemalion
B. Polysiphonia
C. Gelidium
D. Batrachospermum

Answer

To solve the question "Which of the following is a red alga that is not red?" we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: We need to identify a red alga (a member of the red algae group) that does not exhibit the typical red coloration.

2. **Review the Options**: The options provided are:
- A) Namaleon
- B) Polysiphonia
- C) Gelidium
- D) Batrachospermum

3. **Identify the Characteristics of Each Option**:
- **Namaleon**: This is a type of red alga and is typically red in color.
- **Polysiphonia**: This is also a red alga and is known for its red pigmentation.
- **Gelidium**: Another member of the red algae, which is red in color.
- **Batrachospermum**: This alga is classified as a red alga, but it has a unique coloration. It can appear dark violet in deep water and olive green in shallow water.

4. **Determine the Correct Answer**: Since Batrachospermum can appear in colors other than red, it fits the criteria of being a red alga that is not red. Therefore, the correct answer is **D) Batrachospermum**.

### Final Answer:
The red alga that is not red is **Batrachospermum**.

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