The correct option is D Ribosomes
Polyribosomes (or polysomes) also known as ergosomes are a cluster of ribosomes, bound to a mRNA molecule. Polysomes are functional unit of protein synthesis. 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. The first 5-30 amino acids polymerized encode a signal peptide, a molecular message that is recognized and bound by a signal recognition particle.