70 S ribosomes occur in

Options

A. Bacteria
B. Mitochondria
C. Chloroplasts
D. All the above

Answer

**Step-by-Step Solution:**

1. **Understanding Ribosome Types:**
- Ribosomes are classified into two main types based on their sedimentation coefficients: 70S and 80S.
- The 'S' stands for Svedberg units, which measure the rate of sedimentation during centrifugation, indicating the size and density of the ribosomes.

2. **Identifying Where 70S Ribosomes Are Found:**
- 70S ribosomes are primarily found in prokaryotic cells (like bacteria).
- In eukaryotic cells, 70S ribosomes are located specifically in the mitochondria and chloroplasts.

3. **Conclusion:**
- Since 70S ribosomes are found in both prokaryotes (bacteria) and eukaryotes (in mitochondria and chloroplasts), the correct answer to the question "70S ribosomes occur in" is all of the above options provided in the question.

4. **Final Answer:**
- Therefore, the answer is that 70S ribosomes occur in bacteria, mitochondria, and chloroplasts, making option 4 the correct choice.

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