Answer :
A function f maps an element from one domain to a unique range of elements.
Let:
[tex]\begin{gathered} x=\text{domain} \\ y=\text{Range} \\ \end{gathered}[/tex]Since for a given input value yields four output values:
[tex]\begin{gathered} y=4x \\ So\colon \\ y\ne x \\ \text{For:} \\ x\in R \end{gathered}[/tex]Therefore it is true