For the equilibrium system shown below, which of the following will shift the equilibrium to the left?
Cl2 (g) + 3 O2 (g) <---> 2 ClO3 (g) + 154.6 kJ
a. Increasing the pressure on the system
b. Raising the temperature of the system
c. Decreasing the volume of the system
d. Removing ClO3 from the system