C. When energy in the atom is released, a photon is emitted by the atom.
What happens when atom release energy?
When electron of an atom gains energy, it jumps to higher energy level, but when the electrons release energy, they return to the ground state by releasing the extra energy it absorbed in the form of photons.
Thus, when energy in the atom is released, a photon is emitted by the atom.
Learn more about photons here: https://brainly.com/question/15946945
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