Which of the following statements about the molecular arrangement of actin and myosin in myofibrils is incorrect? (i) Each actin (thin filament) is made of 2F (filamentous) actins. (ii) F-actin is the polymer of G (globular) actin. (iii) 2F-actins are twisted into a-helix. (iv) Two strands of tropomyosin (protein) lie in the grooves of F-actin. (v) Troponin molecules (complex proteins) are distributed at regular intervals on the tropomysin. (vi) Troponin forms the head of the myosin molecule. (vii) The myosin is a polymerised protein.

• A. (i), (iii), (vii)
• B. (ii), (iv) and (v)
• C. Only (vi)
• D. Only (iii)