Let's analyze each option to find what best fit as an answer:
A - the function of a catalyst is to lower the energy of activation in a reaction, causing it to occur in a faster way. Since this question is not much about energy or kinetics, this would be the best fit, adding a catalyst or not adding it would not be too influential in the shift of the reaction.
B - Increasing the pressure in a reaction containing gases will mostly favor the side with a lower value of moles, smaller amount of moles = less pressure, so if we add more pressure, the reaction will shift towards the side of the products
C - If we treat heat as a reactant, if we add more temperature, it will shift towards the products, to counteract this increase of temperature
D - Adding reactants will favor the reaction to shift towards the products
Therefore the answer is letter A