The Specific Colors of Light Emitted by an Atom in a Hot

The specific colors of light emitted by an atom in a hot, thin gas (e.g., in a neon tube, a fluorescent bulb, or a gas cloud in space) are caused by

A) an electron dropping into the nucleus, producing small nuclear changes.
B) electrons jumping to lower energy levels, losing energy as they do so.
C) protons jumping from level to level.
D) vibrations of the electrons within the atom.