Which of the following statements about the molecular arrangement of actin in
myofibrils is incorrect?
1\. Each actin (thin) filament is made of two ' \(\mathrm{F}\) ' (filamentous)
actins helically wound to each other.
2\. Each ' \(\mathrm{F}\) ' actin is a polymer of monomeric ' \(\mathrm{G}\) '
(Globular) actins.
3\. Two filaments of another protein, tropomyosin also runs close to the 'F'
actins throughout its length.
4\. A complex protein troponin is distributed at regular intervals on the
tropomyosin.
(a) 1 and 2 only
(b) 3 only
(c) Only 4
(d) None of these