Which of these describes $f : \mathbb{R} \to \mathbb{R}$, $f(x) = \lvert x \rvert$?

Explanation

1. 01

   $f(-3) = f(3) = 3$: not one-one.

2. 02

   $\lvert x \rvert$ is never negative, so $-1$ is not reached: not onto.