Answer:
A
Step-by-step explanation:
N2(g) + 3H2(g) -> 2NH3(g)
According to Le Chatelier's principle, and since H2(g) is on the left side and a reactant, if it's concentration is increased, the equilibrium shifts to the right and the forward reaction is favoured, leading to the production of more NH3(g). The rate of the forward reaction increases.
As the concentration of H2(g) is increased, the concentration of the other reactant, N2(g) decreases as more of it is used up to react with the excess H2(g)