麻烦给一些能决定句子时态的单词例如,句子有ago,那么这个句子就一定是过去式．．并说明决定什么时态,

一般过去时:带有确定的过去时间状语:yesterday,two days ago,last year,the other day,once upon a time,just now,in the old days, before liberation,When I was 8 years old, used to,
过去进行时： 过去某个时刻正在进行：then,at that time,yesterday,at nine ,last night
一般将来时： 时间状语：tomorrow,before long,the day after tomorrow,soon,this afternoon,this year,next week(month,year, summer) in the (near)future,in two weeks(days...),some day
现在完成时： 表示过去已经开始，持续到现在，表示一段时间的状语：
lately,recently,these days,in the past few days,during the last two weeks,since,since 1991,for a long time,for a month,
so far,up to now

一般现在时 usually ,often, always
现在进行时 listen, look ,watch,now
过去进行时 from 9 to 10,this time yesterday,when,
一般过去时 last week,yesterday
过去完成时 before, by
现在完成时 yet ,already,since,for ,ever just,never
一般将来时 tomorrow,the day after tomorrow

already,since,ever