现在完成时表示的动作或状态发生在现在时间以前的某个未明确指出的过去时间内,和它连用的时间状语要与现在时间有关,不能是明确地表示过去的时间状语。
a.不确定的过去时间状语:already, yet, before, recently, lately等
I've seen the film before.
Have you been there lately?
b.频度时间状语:often, sometimes, ever, never, once, rarely等
We have never heard of that.
He has sometimes played tennis.
Big Ben has rarely gone wrong.
c.包含现在时间在内的时间状语:now, just, today, this morning, this week, this year等
I have just finished the letter now.
You have just missed the bus.
Has he done much work today?
already常用于肯定句,置于句中。yet常用于否定句和疑问句,置于句末。但already有时也可用在疑问句中暗示惊讶的心情。
Have you eaten your dinner already?