What will be output in the following code?

public class Mystery $\{$

public static void main$($String$[]$ args$)\{$

String x $=$ "What's up$?"$;

displayString$($x$)$;

return;

$\}$

public static void displayString $($String x$)\{$

System.out.println$($x$)$;

$\}$

$\}$

Group of answer choices

A compiler error will occur because Java is case sensitive and String must be spelled string.

What's up$?$

x