Red snow is caused by

Options

A. stigma
B. chloroplast
C. hypnospore
D. aplanospore

Answer

**Step-by-Step Solution:**

1. **Understanding the Phenomenon**: The question asks about the cause of "red snow." This phenomenon is characterized by snow that appears red in color.

2. **Identifying the Organism**: The red color in snow is primarily due to a specific type of algae. This algae is known as *Chlamydomonas nivalis*.

3. **Role of Hypnospore**: In *Chlamydomonas nivalis*, there are asexual spores called hypnospores. These spores are non-motile and can develop a red pigment.

4. **Pigment Production**: The red pigment produced by *Chlamydomonas nivalis* is called hematochrome. This pigment is responsible for the red coloration of the snow.

5. **Environmental Conditions**: *Chlamydomonas nivalis* thrives in cold environments, particularly in polar and glacial regions. It grows well in freezing water, and as the ice melts, it becomes more visible, contributing to the red appearance of the snow.

6. **Conclusion**: Therefore, red snow is caused by the presence of the algae *Chlamydomonas nivalis*, specifically due to the red pigment hematochrome produced by its hypnospores.

**Final Answer**: Red snow is caused by *Chlamydomonas nivalis*.

---