In a Geiger Counter, Which Is Used to Detect Radioactivity

In a Geiger counter, which is used to detect radioactivity, a particle produced by radioactive decay ________

A) ionizes an inert gas to produce a pulse of electrical current.
B) heats up an inert gas to produce a temperature pulse.
C) excites a phosphor to produce a pulse of visible light.
D) hits a metal plate to produce a voltage pulse.
E) hits a metal plate, vaporizing atoms, to produce a pressure pulse.