The ribosomes of the chloroplasts are-

Options

A. Smaller than the cytoplasmic ribosomes
B. Bigger than the cytoplasmic ribosomes
C. of similar size to the of cytoplasm's
D. size of ribosomes cannot be measured

Answer

### Step-by-Step Solution:

1. **Understanding Ribosomes**: Ribosomes are cellular structures responsible for protein synthesis. There are two main types of ribosomes based on their size and sedimentation rates: 70S and 80S.

2. **Identifying Ribosome Types**:
- **70S Ribosomes**: These are found in prokaryotes, chloroplasts, and mitochondria. They consist of a small subunit (30S) and a large subunit (50S).
- **80S Ribosomes**: These are found in the cytoplasm of eukaryotic cells and consist of a small subunit (40S) and a large subunit (60S).

3. **Comparing Sizes**:
- Since chloroplasts contain 70S ribosomes, we can compare this with the 80S ribosomes found in the cytoplasm of eukaryotic cells.
- The 70S ribosomes are smaller than the 80S ribosomes.

4. **Evaluating the Options**:
- **Smaller than cytoplasmic ribosome**: This is true because 70S (chloroplast ribosomes) are indeed smaller than 80S (cytoplasmic ribosomes).
- **Bigger than cytoplasmic ribosome**: This is false.
- **Similar size of cytoplasm**: This is also false.
- **Size of ribosome cannot be measured**: This is false because ribosome sizes can be measured using techniques like centrifugation.

5. **Conclusion**: The correct answer is that the ribosomes of the chloroplasts are smaller than cytoplasmic ribosomes.