Answer: Since the independent variable x is not the exponent, y = 3x^3 is not an exponential function (choice D)
Exponential functions are something like y = 2^x where the variable is in the exponent (ie the exponent isnt a fixed number). What is given here, y = 3x^3, is a cubic function. You can also call this a power function. Power functions are of the form a*x^b, where a & b are constants.