During that process of being exposed to air and water while being left outside or in the elements for an extended period of time, a variety of different types of rusts can form, but the most common form is Fe2O3. Rust only forms on the outside of a metal surface because it requires exposure of oxygen and water to rust.
On returning to lowest energy state which is stable, it releases energy in the form of light. Hence, option A that is the electron releases energy in the form of light on falling to lower energy state from excite state.
