The contractile proteins in a muscle are actin and myosin. Actin and myosin are the two key proteins that work together to enable muscle contraction. Actin is a thin filament protein that attaches to a structure called Z-line, while myosin is a thick filament protein that contains small projections called cross-bridges. During muscle contraction, the cross-bridges of myosin bind to actin filaments, causing them to slide past each other. This sliding action shortens the muscle fibers and results in muscle contraction. Tropomyosin and troponin are regulatory proteins that control the interaction between actin and myosin, but they are not directly involved in the muscle contraction process. Therefore, option 1 (actin and myosin) is the correct answer.