According to leChatelier's principle the equilibrium will be displaced to compensate any modifications to the equilibrium.
The text says it is an exothermic reaction, therefore decrease the temperature will force the equilibrium to the righthand side.
They also said that the number of molecules is greater on the product side, which means that when the reaction moves to the right side the total pressure of the system will also increase. therefore decreasing the pressure will force the reaction to the right hand side.
This gives us option A as the right answer