The parent function f(x) = log_3(x) has two important values that we can find.
log_3(1) asks "3^? = 1," which we know is 0. So, log_3(1) = 0, which means (1,0) is a point on the graph for the parent function.
log_3(3) asks "3^? = 3" which we know is 1. So, log_3(3) = 1, which means (3,1) is a point on the graph for the parent function.
Now, we look at the graph they gave us and we see that our two points have moved upward 2 units. Now, (1,2) and (3,3). The transformation appears to be f(x) + 2, as you have selected.