C. Pressure will decrease because
To decide the direction in which an equilibrium reaction will go, you must calculate
The two expressions are similar, but
We usually talk of
The system has "just enough products" to be at equilibrium.
The system must react to create more products, that is, it must move to the right.
However, every time we create one mole of product, we remove two moles of reactants.
The number of particles in the flask decreases, so the pressure in the flask must also decrease.