Answer:
Energy
Step-by-step explanation:
Paper is oxidized in the presence of oxygen. This reaction however proceeds very slowly until energy is supplied to the system. This implies that the reaction is not spontaneous at room temperature. A spontaneous reaction takes place without any need for external supply of energy.
The need for supply of external energy must be as a result of the high activation energy required for the reaction to go to completion. If a chemical reaction has a high activation energy, it will require an external supply of energy in order for such reaction to occur.