This function is an exponential function that is also asymptotic to the y axis. Asymptotic means that a function approaches a number at the x or y axis but not necessarily touching it. In this case, the function is asymptotic to y =0. using trial and error, we can see that for any values of b the function is really increasing for a certain period. However, when x is ranging on the negative values, the graph begins to show downward directions. The answer here is C. b>1 as shown in the attached graph as an example.