Focus

The general syntax to overload the stream insertion operator, $<<,$ is $\_\_\_\_.$

friend ostream& operator$<<($ostream&$,$ const className&$)$;

friend ostream& operator $<<($ostream&$,$ const className$)$;

friend stream& operator$<<($stream&$,$ const className&$)$;

friend ostream operator$<<($ostream$,$ const className&$)$;