Site of formation of immature ribosomal subunits in a eukaryotic cell is :

Options

A. nucleus
B. nucleolus
C. nuclear pore complex
D. cytoplasm

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the site of formation of immature ribosomal subunits in a eukaryotic cell.

2. **Identifying the Options**: The options provided are:
- a) Nucleus
- b) Nucleus (repeated)
- c) Nuclear pore complex
- d) Cytoplasm

3. **Analyzing Each Option**:
- **Cytoplasm**: This is primarily where mature ribosomes are found, especially on the rough endoplasmic reticulum. Therefore, this option is not correct for immature ribosomal subunits.
- **Nuclear Pore Complex**: This structure facilitates the transport of molecules between the nucleus and cytoplasm but is not the site of ribosomal subunit formation. Thus, this option is also incorrect.
- **Nucleus**: While the nucleus is involved in the formation of ribosomal components, it is not the specific site where immature ribosomal subunits are formed.
- **Nucleolus**: This is a distinct region within the nucleus that is non-membranous and is specifically responsible for the transcription of ribosomal RNA (rRNA). This rRNA combines with proteins to form the immature ribosomal subunits.

4. **Conclusion**: The correct answer is the **Nucleolus**, as it is the site of formation of immature ribosomal subunits in a eukaryotic cell.

**Final Answer**: Nucleolus

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