Which of the Following Events Occurs During the Lag Phase

Multiple Choice

Which of the following events occurs during the lag phase of a muscle twitch?

A) Muscle fibers shorten.
B) Cross-bridges form, move, release, and reform many times.
C) The action potential is propagated from presynaptic to postsynaptic membrane.
D) Ca²⁺ are pumped back into the sarcoplasmic reticulum.
E) All of these events occur in the lag phase.