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 predominantly exhibit a red color.

2. **Identifying the Pigment**:
- The red color in rhodophytes is primarily due to the presence of a pigment called phycoerythrin.

3. **Function of Phycoerythrin**:
- Phycoerythrin has a unique property; it absorbs light in the blue-green wavelengths of the light spectrum.

4. **Light Absorption and Reflection**:
- While phycoerythrin absorbs blue-green light, it reflects red light, which is why rhodophytes appear red to our eyes.

5. **Growth Depth of Rhodophytes**:
- Rhodophytes typically grow at significant depths in aquatic environments, where only certain wavelengths of light penetrate.

6. **Evaluating the Options**:
- When considering the provided options, the most accurate explanation for the red color of rhodophytes is that they absorb blue-green light due to their depth in the water, which is captured by phycoerythrin.

7. **Conclusion**:
- Therefore, the correct answer is that light reaching great depths in water is primarily in the blue-green region of the spectrum, which is absorbed by phycoerythrin, resulting in the red color of rhodophytes.