Which microorganism do you not need a microscope to look at?

Options

A. Chlamydomonas
B. Rhizobium
C. Agaricus
D. Volvox

Answer

To determine which microorganism you do not need a microscope to look at, we can analyze the given options: Chlamydomonas, Rhizobium, Agaricus, and Wolvox.

### Step-by-Step Solution:

1. **Understanding the Size Limitations of the Human Eye**:
- The human eye can see objects that are about 0.1 mm (100 micrometers) in size. Anything smaller than this requires a microscope to be viewed.

2. **Analyzing Each Option**:
- **Chlamydomonas**: This is a single-celled green algae that typically ranges from 10 to 30 micrometers in size. Therefore, it is smaller than what the human eye can see and requires a microscope.
- **Rhizobium**: This is a genus of bacteria that is also single-celled and usually ranges from 0.5 to 5 micrometers in size. It is much smaller than 0.1 mm and cannot be seen without a microscope.
- **Wolvox**: This is a type of green algae that can form colonies, but the individual cells are still in the micrometer range (about 50 to 100 micrometers). While some colonies might be visible, they are not consistently visible to the naked eye.
- **Agaricus**: This is a genus of fungi that includes mushrooms. Agaricus species can grow quite large, often exceeding 1 cm in size, making them visible to the naked eye.

3. **Conclusion**:
- Among the options provided, **Agaricus** is the microorganism that you do not need a microscope to look at, as it can be seen and even held in your hand.

### Final Answer:
**Agaricus** is the microorganism you do not need a microscope to look at.