Final answer:
The three proteins that make up the thin filaments of skeletal muscle are actin, tropomyosin, and troponin, which work together to control muscle contractions.
Step-by-step explanation:
The three proteins that comprise thin filaments in skeletal muscle are actin, tropomyosin, and troponin. Actin is the primary component of the thin filament, forming long strands that are essential for muscle contraction. Tropomyosin and troponin are regulatory proteins that control the interactions between actin and myosin filaments. When a muscle is at rest, tropomyosin blocks the binding sites on actin to prevent interaction with myosin, and troponin, which has three subunits, regulates this process by binding to tropomyosin, actin, and calcium ions (Ca²+).