9) B

Firstly, catalysts do not affect the equilibrium position and so, 1 is incorrect. This rules out options A, D and F.

Adding more ammonia will favour the forward reaction, which desirable. So 2 is correct. This rules out option C.

Increasing the pressure will favour the forward reaction, which will increase the yield of salt. So, 3 is correct.

Increasing the temperature will favour the backward endothermic reaction and hence, the salt yield will decrease. So 4 is incorrect and this rules out option E.