The function that represents exponential decay is not among the options provided. The function y = -2x represents a linear relationship, not exponential decay.
Exponential decay is characterized by a decreasing trend where the values decrease rapidly at first and then gradually approach zero but never reach it. The general form of an exponential decay function is y = a * e^(kx), where "a" is the initial value and "k" is a negative constant.
If you provide the options you have available, I can help identify the function that represents exponential decay from those options.