Ribosomes are chemically composed of :-

Options

A. RNA only
B. proteins only
C. Lipid only
D. RNA and protein

Answer

### Step-by-Step Solution:

1. **Understanding Ribosomes**: Ribosomes are essential cellular structures involved in protein synthesis. They are found in both prokaryotic and eukaryotic cells and are not membrane-bound.

2. **Composition of Ribosomes**: Ribosomes are made up of two main components: ribosomal RNA (rRNA) and proteins. This combination allows them to perform their function in protein synthesis effectively.

3. **Subunits of Ribosomes**: Ribosomes consist of two subunits:
- The larger subunit
- The smaller subunit
In prokaryotic cells, ribosomes are referred to as 70S ribosomes, while in eukaryotic cells, they are referred to as 80S ribosomes.

4. **Conclusion**: Given that ribosomes are composed of both RNA and proteins, the correct answer to the question is "RNA and protein."

### Final Answer:
Ribosomes are chemically composed of RNA and protein.