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同学好
她离开两天了，可以翻译成：She's been away for two days.
不可以用she has left two days，因为leave是瞬间动词，动作一产生就结束了，没有持续性。不可以和一段时间连用。

常用的瞬间动词有open, close, finish, begin, come, go, arrive, reach, get to, leave, move, borrow,buy,die,etc
现在完成时中如果用瞬间动词，一般其后不跟表示时间段的时间状语。
我们可以说the dog has died.但我们不可以说the dog has died for several days.此时需要把非延续性动词die变成延续性动词be dead。据此句子转变成the dog has dead for several days.是可以的。

常用的这种需转换的还有
leave→be away, borrow→keep, buy→have, begin/start→be on, die→be dead, move to→live in, finish→be over, join→be in/be a member of, open sth.→keep sth. open, fall ill→be ill, get up→be up, catch a cold→have a cold。

希望能帮助到你，祝学习愉快！