Prokaryotic cells are the primitive cells which lack membrane-bound organelles and nucleus. Ribosomes are the smallest cell organelles which are not bounded by the membrane and thus, found in prokaryotic cells. Ribosome plays a vital role in protein synthesis as they consist of protein and RNA. They are located freely in the cytoplasm and attached to the rough endoplasmic reticulum. Prokaryotic ribosomes are the 70s. So, the correct answer is option C.