The correct answer states its C which i understand why since doubling the intiial volume of SO2 is equivilent to doubling the intial moles of SO2 hence the moles of SO3 produced will also increase and hence pressure exerted shld be higher than before which is not reflected by the graph. However, why is D not a possible answer? When temperature increases, the reactant particles will gain energy and cause rate of reaction to increase which is reflected by the graph here. But the SO3 particles produce will also be more active compared to lower temperature in experiment 1, hence shouldnt it exert a higher pressure than experiment 1? which in this case is not shown on the graph.