Refer to the Figure Showing a Neuromuscular Junction

Multiple Choice

Refer to the figure showing a neuromuscular junction. Which event is occurring at position 5?

A) Acetylcholine molecules are entering the postsynaptic cell.
B) Ca²⁺ channels open after acetylcholine binding occurs.
C) Charged acetylcholine molecules cause a graded potential in the postsynaptic membrane.
D) The motor end plate is depolarized by the influx of Na⁺.
E) Acetylcholinesterase breaks down acetylcholine, and the channel closes again.