The correct answer is ribosomes. Ribosomes are organelles that are responsible for the synthesis of proteins in cells. They read the genetic code in messenger RNA (mRNA) and assemble the corresponding amino acids into a polypeptide chain, which is the primary structure of a protein. Ribosomes are composed of two subunits, a large subunit and a small subunit, and are found in both prokaryotic and eukaryotic cells.