If f(x)=xx−1f(x) = \frac{x}{x-1}f(x)=x−1x, which of the following is equal to f(f(f(x)))f(f(f(x)))f(f(f(x)))?
xx−1\frac{x}{x-1}x−1x
xxx
11−x\frac{1}{1-x}1−x1
x−1x\frac{x-1}{x}xx−1