The event(s) that induce the contraction of a muscle fiber is/are the
a. entry of calcium ions into the cytoplasm of the muscle fiber.
b. entry of chloride ions into the cytoplasm of the muscle fiber.
c. release of acetylcholine onto the postsynaptic membrane.
d. separation of the actin and myosin filaments.
e. movement of potassium ions into the muscle fiber.
Answer: a. entry of calcium ions into the cytoplasm of the muscle fiber.
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