Concept:Muscle proteins are contractile proteins that help in movement.Explanation:Myosin is a contractile protein present in muscles.It works with actin to bring about muscle contraction.Keratin is a structural protein found in hair, nails, and skin.Legumelin is a storage protein found in legumes.Insulin is a protein hormone that regulates blood glucose levels.Therefore, the protein of muscles is myosin.Answer:Option B: Myosin