Answer is: A. adding heat to the product mixture.
Balanced chemical reaction:
CO(g) + 3H₂(g) ⇄ CH₄(g) + H₂O(g); ΔH = -206.1 kJ.
This reaction is exothermic, which means that heat is released.
According to Le Chatelier's principle when the reaction is exothermic heat is included as a product and when the temperature increased, the heat of the system increase, so the system consume some of that heat by shifting the equilibrium to the left.
