The transition of an electron from an excited energy state to the ground state always results in a. the absorption of energy b. the emission of electromagnetic radiation d. an increase in the energy of the electron c. the emission of visible light

The transition of an electron from an excited energy state to the ground state always results in B. the emission of electromagnetic radiation.

The electron is going from a high-energy state to one of low energy, so it emits this excess energy as electromagnetic radiation. This may be visible light, but it may also not be visible to our eyes.