一般现在时 he is a student
现在进行时 he is watching tv
一般过去时 he was a stdent
将来时 he will be a stdent
完成时 he has been a stdent for a long time
完成进行时 he has been studying english for a long time
过去进行时 he was going to go shoping
过去完成 he had been a student