现在完成时标志性词语

1.already 用在肯定句中：
I have already finished my homework.
2.ever 多用于疑问句、否定句、和表示条件的附属句子：
Have you ever seen something like this?
No such person ever existed.
If you ever see Tom,give him my kind regards.
3.never 本身就是否定意义的词：
I never had so many problems.
4.yet 可以用在否定句和疑问句当中：
They had not yet come.
Could you please explain why our orders haven't arrived yet?
5.just 一般用在肯定句和现在完成时里：
I just got back from the store.
He has received a just punishment.
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