Rhodophyta are commonly called red algae because of the predominance of the which pigment in their body.

Options

A. r-phycoerythrin
B. c-phycoerythrin
C. r-phycocyanin
D. c-phycocyanin

Answer

**Step-by-Step Solution:**

1. **Identify the Group:** The question refers to Rhodophyta, which is a class of algae commonly known as red algae.

2. **Understand the Color:** The name "red algae" suggests that these organisms have a predominant red color.

3. **Determine the Pigments:** Algae contain various pigments that contribute to their color. In the case of red algae, we need to identify which pigment is primarily responsible for the red coloration.

4. **List the Pigments:** The main pigments found in red algae include:
- Chlorophyll A
- Chlorophyll D
- R-phycoerythrin
- C-phycoerythrin
- R-phycocyanin
- C-phycocyanin

5. **Identify the Key Pigment:** Among these pigments, R-phycoerythrin is known to be the pigment that gives red algae their characteristic red color.

6. **Conclusion:** Therefore, Rhodophyta are commonly called red algae because of the predominance of the pigment R-phycoerythrin in their body.

**Final Answer:** R-phycoerythrin

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