詳解：當 \(x\) 趨近 0 的左極限時，可假設 \(x =  - \varepsilon (\varepsilon \) 表非常微小的數字)

\( \lim\limits_{x \to {0^ - }} \frac{{\left| x \right| - x}}{x} = \frac{{\varepsilon  - ( - \varepsilon )}}{{ - \varepsilon }} = \frac{{2\varepsilon }}{{ - \varepsilon }} =  - 2\)

或這樣想:當 \(x\) 趨近0的左極限時， \(x < 0\) ， \(\left| x \right| =  - x\)

\(\lim\limits_{x \to {0^ - }} \frac{{\left| x \right| - x}}{x} = \lim\limits_{x \to {0^ - }} \frac{{ - x - x}}{x} =  - 2\)

故選(A)