Nuclear membrane is absent in

Options

A. Agaricus
B. Volvox
C. Nostoc
D. Penicillium

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks which organism lacks a nuclear membrane. The options provided are Agaricus, Volvox, Nostoc, and Penicillium.

2. **Identifying Characteristics of Prokaryotes**: Prokaryotes are organisms that do not have a true nucleus. This means they lack a nuclear membrane surrounding their genetic material. They also do not possess membrane-bound organelles.

3. **Identifying Characteristics of Eukaryotes**: Eukaryotes, in contrast, have a true nucleus with a nuclear membrane and possess membrane-bound organelles such as mitochondria and chloroplasts.

4. **Analyzing the Options**:
- **Agaricus**: This is a genus of fungi, which are eukaryotic organisms. Therefore, Agaricus has a nuclear membrane.
- **Volvox**: This is a genus of green algae, which also falls under eukaryotes. Thus, Volvox has a nuclear membrane.
- **Nostoc**: This is a genus of cyanobacteria (often referred to as blue-green algae), which are prokaryotic organisms. Therefore, Nostoc lacks a nuclear membrane.
- **Penicillium**: This is another genus of fungi and is also eukaryotic, meaning it has a nuclear membrane.

5. **Conclusion**: Based on the analysis, the organism that lacks a nuclear membrane is **Nostoc**. Therefore, the correct answer is option C: Nostoc.