A function $f:S\rightarrow T$ such that $f(s)=f(s')$ implies $s=s'$ is called *one-to-one* (also written $1-1$).

One-to-one functions are also called injective functions, and they occur in Abstract Algebra, for example in the context of linear transformations of vector spaces or of homomorphisms of groups (don't worry if you haven't met such examples yet).

Which of the following functions are **NOT** one-to-one?

By ${\mathbb C}$, we mean the complex numbers, and $i=\sqrt{-1}$.

Select **ALL** that apply.