The smallest living cells/ organisms :

Options

A. have chlorophyll-a
B. cause only animal diseases
C. do not have cell wall
D. have only one type of nucleic acid

Answer

To determine the smallest living cells or organisms, we need to analyze the characteristics of the options provided. Here’s a step-by-step solution:

### Step 1: Identify the smallest living cells
- The smallest living cells are known to be **mycoplasma**. They are a type of bacteria that lack a cell wall and are known for their small size.

### Step 2: Analyze the options given
1. **Chlorophyll-A**: This is a pigment found in plants and some microorganisms, specifically in the thylakoid membranes of chloroplasts. It is not related to the characteristics of mycoplasma.
- **Conclusion**: This option is incorrect.

2. **Cause only animal diseases**: Mycoplasma can cause diseases in both plants and animals, not exclusively animal diseases.
- **Conclusion**: This option is incorrect.

3. **Do not have a cell wall**: Mycoplasma is unique among bacteria because it does not have a cell wall. Instead, it has a plasma membrane that serves as the outer boundary of the cell.
- **Conclusion**: This option is correct.

4. **Have only one type of nucleic acid**: Mycoplasma, like other living organisms, contains both DNA and RNA. Therefore, this statement is incorrect.
- **Conclusion**: This option is incorrect.

### Final Answer
The correct answer is **Option 3: Do not have a cell wall**.

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