Which is wall -less and smallest living cell

Options

A. Algae
B. Bacteriophage
C. Cyanobacteria
D. Mycoplasma.

Answer

### Step-by-Step Solution:

1. **Identify the Question**: The question asks for the smallest living cell that is wall-less.

2. **Understand the Options**: The options provided are:
- Algae
- Bacteriophages
- Cyanobacteria
- Mycoplasma

3. **Analyze Each Option**:
- **Algae**: These are eukaryotic organisms and have cell walls, so they cannot be the answer.
- **Bacteriophages**: These are viruses that infect bacteria, not living cells, so they are not the answer.
- **Cyanobacteria**: These are photosynthetic bacteria that have cell walls, so they are not wall-less.
- **Mycoplasma**: This is a type of bacteria that lacks a cell wall, making it wall-less.

4. **Confirm Characteristics of Mycoplasma**:
- Mycoplasma is known as the smallest living cell.
- It is referred to as PPLO (Pleuropneumonia-like organism) because it can cause pneumonia.
- Mycoplasma can survive without oxygen and can have parasitic or saprophytic modes of nutrition.

5. **Conclusion**: Based on the analysis, the smallest wall-less living cell is **Mycoplasma**.

### Final Answer:
The smallest wall-less living cell is **Mycoplasma**.

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