我们用将来完成时态来形容一个在未来特定的一个时间已经完成的动作。

We use the future perfect tense to talk about an action that will be completed at a given time in the future.

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到2011年的时候，上海已经举办好了世博会。(用将来完成时态)。

By 2011, Shanghai will have held the World Exposition.

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我们用将来完成进行时态来形容一个行动在未来特定的时间里已进行多久了。

We use the future perfect continuous tense to talk about how long an action will be going on at a future time.

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