What is the exponential function modeled by the following table? 
x f(x)
3  8 
4 16 
5  32
A. f(x) = 2^x
B. f(x) = x^2 
C. f(x) = x^3 
D. f(x) = 3^x 
                                             
                                          
                                          
                                        
											