I CAN’T FIND MY KEY ANYWHERE. I ……….HAVE LEFT IT ON THE TRAIN. I AM...

9. - ON TAP KIEM TRA 1 TIET SO 2
ON TAP KIEM TRA 1 TIET SO 2

9. I can’t find my key anywhere. I ……….have left it on the train. I am not sure.( must /

might / should / can)