Which of these functions has a derivative of 000 for all values of xxx?
f(x)=xf(x) = xf(x)=x
f(x)=ef(x) = ef(x)=e
f(x)=1/xf(x) = 1/xf(x)=1/x
f(x)=x0f(x) = x^0f(x)=x0