Answer
The addition of $SO_2(g)$ would increase the rate of the reaction.
Work Step by Step
When you add a certain quantity of $SO_2(g)$, the concentration of that is increased. With a larger concentration, more collisions are likely to occur. Therefore, the reaction will occur faster than normally.
According to the Table 7.8, the increase of the reactant concentration is a factor that increases the reaction rate.