The range of a function is the set of values that the function reach with its outputs.
In other words, a number belongs to the range of the function
if there exists a number
belonging to the domain of
such that
.
Looking at your graph, you can see that any value smaller than 2 is not reached by the graph, because the lines are only drawn from 2 upwards.
So, the answer is C, because it is the set of all numbers greater then or equal to 2.