**Explanation:**

Ribosomes are small, non-membrane bound organelles that are involved in protein synthesis. They can be found in both prokaryotic and eukaryotic cells. In eukaryotic cells, ribosomes are present in the cytoplasm as well as on the rough endoplasmic reticulum (RER). However, there are exceptions to this general rule, and ribosomes are absent in certain organelles such as the chloroplasts and mitochondria.

**Non-membrane bound:**
- Ribosomes are non-membrane bound organelles, meaning they are not surrounded by a lipid bilayer like other organelles such as the nucleus or mitochondria.
- They consist of two subunits, a large subunit and a small subunit, which come together to form a functional ribosome.

**Present in the cytoplasm and on RER:**
- Ribosomes can be found in the cytoplasm of cells, where they are involved in the synthesis of proteins that are used within the cell.
- In addition to the cytoplasm, ribosomes can also be found attached to the rough endoplasmic reticulum (RER).
- The RER is involved in the synthesis and packaging of proteins that are destined for secretion or for use in the cell membrane.

**Absent in chloroplast and mitochondria:**
- Ribosomes are absent in certain organelles, such as the chloroplasts and mitochondria.
- Chloroplasts are the organelles responsible for photosynthesis in plant cells, and they contain their own ribosomes that are involved in the synthesis of chloroplast proteins.
- Similarly, mitochondria, known as the powerhouses of the cell, also have their own ribosomes that are involved in the synthesis of mitochondrial proteins.

**Take part in protein synthesis:**
- Ribosomes are the site of protein synthesis in the cell.
- They use the information encoded in mRNA (messenger RNA) to synthesize proteins by linking amino acids together in a specific order.
- This process occurs in two main steps: transcription, where the DNA is transcribed into mRNA, and translation, where the mRNA is used as a template to synthesize proteins with the help of ribosomes.

In conclusion, the correct answer is option C, as ribosomes are absent in chloroplasts and mitochondria, but are present in the cytoplasm and on the rough endoplasmic reticulum (RER).