Le Châtelier's principle states that <em>when there is an dynamic equilibrium, and this equilibrium is disturbed by an external factor, the equilibrium will be shifted in the direction that can cancel the effect of the external factor to reattain the equilibrium.</em>
Increasing the volume of oxygen:
will increase the concentration of oxygen (reactants), so the equilibrium will be shifted to the right side (products side) to suppress the effect of increasing the volume of oxygen.
<em>So, the right choice is: The rate of forward reaction increases.
</em>
