The true statement about ribosomes is `

Options

A. Attached ribosomes synthesise proteins mainly for use inside the cell.
B. Attached ribosomes are 70 S
C. 16S rRNA is absent in 80 S ribosomes
D. All of the above

Answer

To determine the true statement about ribosomes from the given options, let's analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding Ribosome Types**:
- Ribosomes can be classified into two main types based on their size: 70S and 80S.
- 70S ribosomes are typically found in prokaryotes (like bacteria), while 80S ribosomes are found in eukaryotes (like plant and animal cells).

2. **Evaluating the First Option**:
- The first statement claims that attached ribosomes synthesize proteins mainly for use inside the cell.
- However, attached ribosomes (those bound to the endoplasmic reticulum) primarily synthesize proteins that are secreted outside the cell or incorporated into the cell membrane. Therefore, this statement is **false**.

3. **Evaluating the Second Option**:
- The second statement claims that attached ribosomes are 70S.
- This is incorrect because attached ribosomes are typically 80S ribosomes found in eukaryotic cells. The 70S ribosomes are found in prokaryotic cells. Thus, this statement is also **false**.

4. **Evaluating the Third Option**:
- The third statement claims that 16S rRNA is absent in 80S ribosomes.
- This statement is **true**. The 16S rRNA is a component of the 70S ribosome, while the 80S ribosome contains 18S rRNA instead of 16S rRNA.

5. **Evaluating the Fourth Option**:
- The fourth option states "all of the above."
- Since the first two statements are false, this option is also **false**.

### Conclusion:
The only true statement about ribosomes among the given options is the third one: **"16S rRNA is absent in 80S ribosomes."**