Explanation:
a. pressure always favors the side with fewer molecules. in this reaction as both the sides have equal number of molecules, there won't be any change in the position of the equilibrium.
b. when the concentration of the hydrogen gas is increased. more particles would take place in the reaction and so, the rate of reaction would increase favoring the reaction concerning hydrogen gas molecules (backward reaction in this case) therefore, equilibrium would shift to the backward reaction (left).
c. as forward reaction is endothermic, when temperature is increased the equilibrium will shift to the forward reaction (right).
d. catalyst would not have any effect on the position of the equilibrium. it will only increase the rate of reaction.
hope it helps. :)
