A muscle fiber contracts by a sequence of events initiated by the binding of acetylcholine to its receptor. Which of the following is the correct sequence?I - The calcium-troponin complex pulls tropomyosin away from the myosin-binding sites of actin.II - The freed-sites of actin bind to myosin to form cross-bridges.III - Calcium ion binds to the troponin.
A. I, II, and III
B. III, II, and I
C. I, III, and II
D. II, III, and I
E. III, I, and II
Answer: E
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