Which of the following can photosynthesize at low temperature `(-20^@ C)`

Options

A. Bacteria
B. Lichen
C. Yeast
D. Batrachospermum

Explanation

To determine which organism can photosynthesize at low temperatures (as low as -20°C), we can analyze the options provided: bacteria, lichen, yeast, and Betra core spermum.

### Step-by-Step Solution:

1. **Understanding Photosynthesis**: Photosynthesis is the process by which organisms convert light energy into chemical energy, typically using chlorophyll to capture light and convert carbon dioxide and water into glucose and oxygen.

2. **Analyzing the Options**:
- **Bacteria**: Most bacteria do not perform photosynthesis in the same way plants and algae do. While some bacteria can perform a form of photosynthesis, they are generally not adapted to extremely low temperatures.
- **Yeast**: Yeast is a type of fungus that primarily performs fermentation rather than photosynthesis. Yeast does not have the necessary structures for photosynthesis and therefore cannot photosynthesize at any temperature.
- **Lichen**: Lichens are a symbiotic association between fungi and algae (or cyanobacteria). The algal component of lichen can perform photosynthesis, and lichens are known to survive in extreme environments, including very low temperatures. They can photosynthesize even at temperatures as low as -20°C.
- **Betra core spermum**: This option seems to be a misspelling or an obscure reference, but generally, if it refers to a type of plant or organism, it is less likely to be adapted to such low temperatures compared to lichens.

3. **Conclusion**: Based on the analysis, the organism that can photosynthesize at low temperatures (down to -20°C) is **lichen**.

### Final Answer:
The correct answer is **B) Lichen**.