Nuclear membrane is absent in:-

Options

A. chlamydomonas
B. Nostoc
C. mycoplasma
D. both b and c

Answer

To answer the question "Nuclear membrane is absent in:", we need to understand the characteristics of prokaryotic and eukaryotic cells.

### Step-by-Step Solution:

1. **Identify the Types of Cells**:
- Cells are generally classified into two main categories: prokaryotic and eukaryotic.
- Prokaryotic cells (like bacteria) do not have a nuclear membrane, while eukaryotic cells (like plants, animals, and fungi) do have a nuclear membrane.

2. **Understand the Nuclear Membrane**:
- The nuclear membrane, also known as the nuclear envelope, surrounds the nucleus in eukaryotic cells and separates the genetic material from the cytoplasm.
- In prokaryotic cells, the genetic material is not enclosed in a membrane-bound nucleus; instead, it is located in a region called the nucleoid.

3. **Analyze the Given Options**:
- The question likely provides several options, including organisms like Chlamydomonas, Nostoc, and Mycoplasma.
- Chlamydomonas is a type of green algae and is a eukaryote, thus it has a nuclear membrane.
- Nostoc is a cyanobacterium (also known as blue-green algae), which is prokaryotic and does not have a nuclear membrane.
- Mycoplasma is a genus of bacteria, which are also prokaryotic and lack a nuclear membrane.

4. **Determine the Correct Answer**:
- Since the question asks where the nuclear membrane is absent, we identify that both Nostoc and Mycoplasma are prokaryotic and do not have a nuclear membrane.
- Therefore, the correct answer to the question is that the nuclear membrane is absent in both Nostoc and Mycoplasma.

5. **Final Answer**:
- The correct option is D, which states that nuclear membrane is absent in both B (Nostoc) and C (Mycoplasma).