Which statement best describes the conditions for f (x) = a (b) ^x to be a model for exponential growth?

In order for this to be a model of exponential growth, the b term must be greater than 1.

If the b term is between 0 and 1, then it becomes a model for exponential decay as the number will continue to get smaller and smaller for every value of x. Greater than one will continue to grow and therefore be an exponential growth model.