When we have a reaction in equilibrium, a change in temperature, pressure or the concentration of the compounds can shift the reaction towards the reactants or the products.
If we remove one of the compounds and its concentration decreases, the reaction shifts to the side of the compound that decreases its concentration. Therefore, if we remove NH4+ from the solution, the reaction will shift towards NH4+ and there will be more NH4+ formation.
So, the answer will be:
B. [NH4+] would increase.
