Consider the reaction for the combustion of hydrogen below:

2H2 + O2 --> 2H2O

Where would you need to add "energy" to make this reaction complete?

A. in the reactants because the reaction is exothermic
B. in the products because the reaction is exothermic
C. in the products because the reaction is endothermic
D. in the reactants because the reaction is endothermic