The correct option is B Actin, troponin and tropomyosin
Troponin is a component of thin filaments along with actin and tropomyosin and this is the protein complex to which calcium binds to trigger the production of muscular force. One thin filament consists about 400 actin molecules and around 50 molecules of tropomyosin and troponin each.
So, the correct answer is option A.