The smallest living cell is :

Options

A. Virus
B. Viroid
C. Mycoplasma
D. Cyanobacteria

Answer

To solve the question "The smallest living cell is:", we will analyze the options provided and determine which one represents the smallest living cell.

### Step-by-Step Solution:

1. **Understanding the Options**:
- **A. Virus**: Viruses are not considered living cells as they cannot reproduce independently and require a host cell to replicate.
- **B. Viroid**: Viroids are infectious agents composed solely of a short strand of RNA and do not have a cellular structure. They are also not classified as living cells.
- **C. Mycoplasma**: Mycoplasma are the smallest known living cells. They lack a cell wall and can survive in various environments, including those without oxygen.
- **D. Cyanobacteria**: Cyanobacteria are photosynthetic bacteria, but they are larger than Mycoplasma.

2. **Identifying the Smallest Living Cell**:
- Among the options, Mycoplasma is recognized as the smallest living cell. It is approximately 0.2 to 0.3 micrometers in size, which is significantly smaller than other living cells.

3. **Conclusion**:
- Based on the analysis, the correct answer is **C. Mycoplasma**.

### Final Answer:
The smallest living cell is **C. Mycoplasma**.

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