past perfect vs.simple past.Choose the correct verb form.

past perfect vs.simple past.Choose the correct verb form.Sam ___________yesterday.a.left b.has left c.had left d.leavingSam____________when you__________.a.had already left,called b.left already,called c.has left,call d.leaving,calling.Last night I saw an old friend.I____________her in years.a.not seeing b.haven't seen c.hadn't seen d.didn't seeLast month,I visited New York alone,Before that,I___________by myself.a.never traveled b.have never traveled c.never travel d.had never traveledBy the time the movie finished,it_______________raining.a.had stopped b.have stopped c.stopped d.stop