Which one of the following cell organelles is enclosed by a single membrane

Options

A. Chloroplasts
B. Lysosomes
C. Nuclei
D. Mitochondria

Answer

To determine which cell organelle is enclosed by a single membrane, we can analyze the options provided:

1. **Chloroplast**:
- Chloroplasts are involved in photosynthesis and are surrounded by two membranes (an inner and an outer membrane).
- **Conclusion**: Not enclosed by a single membrane.

2. **Lysosome**:
- Lysosomes are cellular organelles that contain digestive enzymes and are responsible for breaking down waste materials and cellular debris.
- They are surrounded by a single membrane.
- **Conclusion**: Enclosed by a single membrane.

3. **Nucleus**:
- The nucleus is the control center of the cell, containing the cell's genetic material.
- It is surrounded by a double membrane known as the nuclear envelope.
- **Conclusion**: Not enclosed by a single membrane.

4. **Mitochondria**:
- Mitochondria are known as the powerhouse of the cell and are involved in energy production.
- They are also surrounded by two membranes (an inner and an outer membrane).
- **Conclusion**: Not enclosed by a single membrane.

After analyzing all the options, we find that the only organelle that is enclosed by a single membrane is the **lysosome**.

### Final Answer:
**Lysosome** is the cell organelle that is enclosed by a single membrane.