A habitat not suitable for primary productivity is

Options

A. cave
B. meadow
C. river bank
D. pond

Answer

### Step-by-Step Solution:

1. **Understanding Habitat**:
- A habitat is defined as a natural environment where various organisms, including plants and animals, coexist. It provides the necessary conditions for life.

2. **Defining Primary Productivity**:
- Primary productivity refers to the rate at which energy is converted by photosynthetic and chemosynthetic autotrophs to organic substances. This process is crucial as it forms the base of the food chain in an ecosystem.

3. **Identifying Photosynthetic Organisms**:
- Photosynthetic organisms, such as plants and algae, are vital for primary productivity as they convert light energy into chemical energy through photosynthesis.

4. **Evaluating the Options**:
- The question provides several habitats, and we need to determine which one is not suitable for primary productivity.

5. **Analyzing Each Option**:
- **Cave**: Caves are natural voids that typically lack sunlight, which is essential for photosynthesis. Therefore, caves do not support primary productivity.
- **Meadows**: Meadows are open fields that can support various plant life and are suitable for primary productivity.
- **River Bank**: River banks are near water sources and can support both aquatic and terrestrial plants, making them suitable for primary productivity.
- **Ponds**: Ponds are freshwater habitats that can support algae and other aquatic plants, indicating they are suitable for primary productivity.

6. **Conclusion**:
- Based on the analysis, the habitat that is not suitable for primary productivity is the **cave**.