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Perfective Aspect 有关完成时态
We use the present perfectto show that something has continued up to the present
They’ve beenmarried for nearly fifty years.
She has lived in Liverpool all her life.
… or is important in the present:
I’ve lostmy keys. I can’t get into the house.
Teresa isn’t at home. I think she has goneshopping.
We use the present perfect continuous to show that something has been continuing up to the present:
It’s been rainingfor hours.
We’ve been waitinghere since six o’clock this morning.
We use the past perfectto show that something continued up to a time in the past:
When George died he and Anne had beenmarried for nearly fifty years.
... or was important at that time in the past:
I couldn’t get into the house. I had lostmy keys.
Teresa wasn’t at home. She had goneshopping.
We use the past perfect continuous to show that something had been continuing up to a time in the past or was important at that time in the past:
Everything was wet. It had been rainingfor hours.
He was a wonderful guitarist. He had been playingever since he was a teenager.
We use will with the perfect to show that something will be complete at some time in the future:
In a few years they will have discovereda cure for the common cold.
I can come out tonight. I'll have finishedmy homework by then.
We use would with the perfect to refer to something that did not happen in the past but would have happened if the conditions had been right:
If you had asked me I would have helpedyou.
I would have helpedyou, but you didn’t ask me.
We use other modals with perfective aspect when we are looking backfrom a point in time when something might have happened, should have happened or would have happened.
The point of time may be in the future:
We’ll meet again next week. We might have finished the work by then.
I will phone at six o’clock. He should have got home by then.
It’s getting late. They should have arrived by now.
He’s still not here. He must have missed his train.
or the past:
I wasn’t feeling well. I must have eaten something bad.
I checked my cell phone. She could have left a message.