Which of the following functions f(x)f(x)f(x) satisfies the property f′(x)=f(x)f'(x) = f(x)f′(x)=f(x) and f(0)=2f(0)=2f(0)=2?
f(x)=exf(x) = e^xf(x)=ex
f(x)=2exf(x) = 2e^xf(x)=2ex
f(x)=e2xf(x) = e^{2x}f(x)=e2x
f(x)=2xf(x) = 2xf(x)=2x