Given that the variable $y$ is a function of the variable $x,$ select ALL options that COULD BE TRUE.

Every $x$ value $($input$)$ is associated with exactly one $y$ value $($output$)$

Every $x$ value $($input$)$ is associated with many $y$ values $($output$)$

Every $y$ value $($output$)$ is associated with many $x$ values $($input$)$

Every $y$ value $($output$)$ is associated with exactly one $x$ value $($input$)$