Given these events: choose the arrangement that lists the events in the order they occur at a neuromuscular junction. (1) Acetylcholine is broken down into acetic acid and choline. (2) Acetylcholine diffuses across the synaptic cleft. (3) An action potential reaches the terminal branch of the motor neuron. (4) Acetylcholine combines with a ligand-gated ion channel. (5) An action potential is produced on the muscle fiber's plasma membrane