The biosynthesis of ribosomal RNA occurs in:

Options

A. Ribosomes
B. Golgi apparatus
C. Microbodies
D. Nucleolus

Answer

To solve the question regarding the biosynthesis of ribosomal RNA, we can follow these steps:

### Step 1: Understand the Question
The question asks where the biosynthesis of ribosomal RNA (rRNA) occurs. We need to identify the correct cellular structure responsible for this process.

### Step 2: Analyze the Options
We have four options to consider:
1. Ribosomes
2. Golgi apparatus
3. Microbodies
4. Nucleolus

### Step 3: Evaluate Each Option
- **Option 1: Ribosomes**
- Ribosomes are the sites of protein synthesis, not rRNA synthesis. They decode mRNA and form peptide bonds.

- **Option 2: Golgi apparatus**
- The Golgi apparatus is involved in the sorting and packaging of proteins. It does not play a role in the synthesis of rRNA.

- **Option 3: Microbodies**
- Microbodies (such as peroxisomes) are involved in various metabolic processes, including lipid metabolism, but not in rRNA synthesis.

- **Option 4: Nucleolus**
- The nucleolus is a dense structure found within the nucleus of eukaryotic cells. It is specifically responsible for the biosynthesis of ribosomal RNA.

### Step 4: Conclusion
Based on the evaluation of each option, the correct answer is **Option 4: Nucleolus**. The nucleolus is the site where ribosomal RNA is synthesized.