We saw some GUI $($Graphical User Interface$)$ Java code in class. How were the UI widgets $$wired$-$up$$ to the functions that were called when a user selected the widget? a$.$ UI widgets automatically call a function based on the name of the widget $($e$.$g$.,$ButtonFileOpen$$ calls $$onButtonFileOpen$\_$Click$()).$ b$.$ UI widgets are connected to functions through a JSON configuration file. c$.$ UI widgets are connected to functions through an XML configuration file. d$.$ UI widgets must be given a function pointer for the $$handler$$ when they are constructed. e$.$ None of the above.