In the atom, the nucleus is charged positive and the electron is charged
negative. So we know that they're attracted to each other. It takes energy
to keep the electron from falling into the nucleus.
-- If you want to drag the electron farther out from the nucleus, you have to
do work on it ... put energy in to it.
-- When the electron loses energy, it falls in closer to the nucleus. The more
energy it loses, the closer to the nucleus it falls.
-- From the list of choices in the question, the electron moving two energy levels
closer to the nucleus loses more energy than any other choice.
