If we have a set of ordered pair (like this table here) we can know if it can represent a function if the numbers on x (the variable that the function depends on) are repeated or not. If they repeat, then is not a function.
In this problem we can see that the amount of cans of repellent used is 0 1 5 4 2 4 3 2. This is our x. You see, of these numbers, 4 and 2 repeat so the answer is no, it cannot be represented as a function of the amount of cans of repellent used.