B. In this reaction, the amount of substance Z participating in the reaction is 0.6 mol. According to the equation, the amount of substance Y participating in the reaction is 32× 0.6 mol = 0.9 mol, and the amount of substance Y in equilibrium is 0.4mol, so the amount of substance Y in the initial reaction is 1.3mol, so b is correct;
C the temperature is constant and the equilibrium constant is constant, so K(A)=K(B), so c is wrong;
D when the equilibrium state changes from a to b, P (a) < P (b), which increases the pressure balance and moves to the positive reaction direction. The positive reaction is exothermic, so the heat released: Q (a) < Q (b), so d is correct;
So choose C.