Which of the following correctly explains why rhodophytes exhibit a red colour?

Options

A. Since most rhodophytes grow at great depths, the chlorophyll can only absorb light in the red area of the spectrum.
B. The wavelengths of light that are absorbed by chlorophyll are passed to phycoerythirn (a red pigment)
C. Phycoerythrin absorbs all the light waves.
D. Light reaching the greatest depth in water is in the blue green region of the spectrum. This light is absorbed by phycoerythrin.

Explanation

### Step-by-Step Solution:

1. **Understanding Rhodophytes**: Rhodophytes, commonly known as red algae, are a group of algae that are characterized by their red color. This color is primarily due to the presence of a pigment called phycoerythrin.

2. **Light Absorption**: Rhodophytes can be found at various depths in the ocean, including areas where light penetration is minimal. As light penetrates water, different wavelengths are absorbed at different depths.

3. **Role of Chlorophyll**: Chlorophyll, the primary pigment in plants, absorbs light primarily in the blue and red wavelengths. However, in deeper waters where rhodophytes are often found, the light that penetrates is predominantly in the blue-green region of the spectrum.

4. **Function of Phycoerythrin**: Phycoerythrin is a pigment that absorbs blue-green light. When rhodophytes absorb this blue-green light, they reflect red light, which is why they appear red to our eyes.

5. **Conclusion**: Therefore, the red color of rhodophytes is due to the absorption of blue-green wavelengths by phycoerythrin, while red wavelengths are reflected.

### Final Answer:
The correct explanation for why rhodophytes exhibit a red color is that phycoerythrin absorbs blue-green light and reflects red light.

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