Answer: A. only II
Step-by-step explanation
When a fraction is elevated into a big number, we get a small number. For example:

Contrarily, when we elevate a whole number into another whole number, we get a big number. For example:

Therefore, if we are searching for exponential growth, the one with growth will be that in which the number is not a fraction. Graphically, we can notice how functions I and III approach 0 as x goes to positive infinity, while function II approaches plus infinity as x increases.