The smallest cell of 0.3 um in length is

Options

A. Ostrich egg
B. Cyanobacteria
C. Bacteria
D. Mycoplasma

Answer

To solve the question about the smallest cell of 0.3 micrometers in length, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: The question asks for the smallest cell, specifically one that measures 0.3 micrometers in length.

2. **Identify the Options**: The options provided are:
- A) Ostrich egg
- B) Cyanobacteria
- C) Bacteria
- D) Mycoplasma

3. **Classify the Cells**:
- **Eukaryotic Cells**: Generally larger in size. For example, the ostrich egg is known to be the largest single cell.
- **Prokaryotic Cells**: Typically smaller than eukaryotic cells. This group includes bacteria, cyanobacteria, and mycoplasma.

4. **Evaluate Each Option**:
- **Ostrich Egg**: This is a eukaryotic cell and is the largest cell, so it cannot be the answer.
- **Cyanobacteria**: A type of prokaryote, but generally larger than 0.3 micrometers.
- **Bacteria**: Also prokaryotic, but not the smallest type.
- **Mycoplasma**: Known to have very small cell sizes, ranging from 0.04 to 0.3 micrometers.

5. **Conclusion**: Since mycoplasma is the only option that fits the criteria of being the smallest cell at around 0.3 micrometers in length, we conclude that the answer is **D) Mycoplasma**.

### Final Answer:
The smallest cell of 0.3 micrometers in length is **Mycoplasma**.