Final answer:
The percent change of the function y = 45(1.39)^x represents a 39% increase in y for each unit increase in x, which is characteristic of an exponential growth function.
Step-by-step explanation:
The student is asking about the percent change of the function y = 45(1.39)^x. The general form of an exponential growth function is y = ab^x, where a is the initial amount (in this case, 45), and b is the base that represents the growth rate. Considering the function given, the growth rate is 1.39. This means that with each increase of 1 in x, the value of y increases by a factor of 1.39, which translates to a 39% increase each time (since 1.39 is equal to 139% as a proportion, where the original 100% signifies no change and the additional 39% indicates growth). Therefore, the correct answer is a 39% increase per unit change in x.