Why Does the Observation of Spectral Emission from a Highly

Why does the observation of spectral emission from a highly ionized atom such as iron, Fe XIV, with 13 electrons missing, indicate very high gas temperatures?

A) The presence of iron means that nuclear fusion must be occurring, and this process needs very high temperatures.
B) Highly ionized atoms must come from high-density regions that can only exist in high temperature gases.
C) Collisions that remove this number of electrons must be very energetic between fast-moving atoms.
D) Photons that will eject these electrons must be very energetic and come from high-temperature gas.