Yield of the product generally depends on - Temperature - Concentration of reactant(s) and product(s) - Pressure As this is an endothermic reaction ( ∆H=+180.7‌kJ‌mol−1 ), so, increase in temperature will shift equilibrium in forward direction to increase yield of NO. Increase in concentration of reactants ( N2 and O2 ) also shifts the equilibrium in forward direction and increase the yield of NO. Hence, (A), (C) and (D) only will increase yield of NO.