The given figure shows two trains running in opposite directions.  Which function’s graph resembles the paths of the trains?

f: R $\rightarrow$ R defined by $f(x) = \left\{ \begin{array}{l l} \large\frac{|x|}{x}, & \quad if\: x \neq 0 \\ 0, & \quad if\: x = 0 \end{array} \right.$