In the use case modeling, each $\_\_\_\_\_\_\_\_\_\_\_\_$ determines an actor's goal.

$1.$

Class

$2.$

Use case

$3.$

object

$4.$

Process

$1.$

$5($five$-$tier$)$ client$/$server

$2.$

$2($two$-$tier$)$ client$/$server

$3.$

$3($three$-$tier$)$ client$/$server

$4.$

n$-$tier client$/$server