What is occurring during this period of a muscle twitch contraction?

A) The muscle action potential sweeps along the sarcolemma and calcium ions are released from the sarcoplasmic reticulum.
B) Ach binds to the ligand gated channels at the motor end plates.
C) The level of Ca²⁺ in the sarcoplasm decreases, because it is being actively transported back into the sarcoplasmic reticulum.
D) Calcium ions bind to Troponin.
E) Power strokes generate contractile force.