What can you assume has happened if an electron moves to a higher energy level

EXPLANATION :

As per the question, the electron has jumped from ground state to higher energy level.

From Bohr's postulate, we know that electron can only move to higher excited state when the energy equivalent to excitation energy has been given to it. Otherwise, the electron can not move from ground state to the excited state.

Hence, it is obvious that the electron might have excited to higher energy level by providing sufficient energy from outside.

The external source might be light of suitable frequency or  any electric or thermal source.

i think its c if i'm wrong