The correct option is C Protein synthesis
Ribosomes are the site for protein synthesis. The surface of the rough endoplasmic reticulum is studded with protein-manufacturing ribosomes. The synthesis of proteins start with the binding of the ribosome on the rough endoplasmic reticulum at the translocon. A ribosome only binds to the RER once a specific protein-nucleic acid complex forms in the cytosol. This special complex forms when a free ribosome begins translating the mRNA of a protein destined for the secretory pathway.