Concept:Ribosomes are the site of protein synthesis. They are made of ribosomal RNA (rRNA) and proteins.Explanation:Each ribosome has two subunits: a large subunit and a small subunit.The large subunit joins amino acids to form a polypeptide chain.The small subunit reads the mRNA sequence.Both subunits contain rRNA and ribosomal proteins.Thus, ribosomes are composed of RNA and protein, not DNA or amino acids.Answer:B. RNA and Protein