[求助]Prep-25

ciduo777 · 发表于 2007-4-21 12:42:00

请教Prep-25:

25. Ozone reaches high concentrations twelve miles above Earth, where it has long appeared that it was immune from human influence; we have now realized, though, that emissions of industrial chlorofluorocarbons deplete the ozone layer.

A) has long appeared that it was immune from

B) has long appeared to have been immune from

C) has long appeared as being immune to

D) had long appeared immune to

E) had long appeared that it was immune to

答案选D.的确相比较而言是最佳选项，可是我不懂怎么理解其中had的用法呢？句中并没有出现一般过去时，也就无所谓“过去的过去”咯吧？迷惑ing……请指教

羽衣草 · 发表于 2007-4-21 13:32:00

请赐教

！

Zeldaw · 发表于 2007-4-21 13:38:00

这是以前的讨论贴，都是问这个问题，lz看看有没有帮助

http://forum.chasedream.com/dispbbs.asp?BoardID=23&replyID=2225913&id=237175&skin=0

http://forum.chasedream.com/dispbbs.asp?BoardID=23&replyID=1990916&id=213324&skin=0

http://forum.chasedream.com/dispbbs.asp?BoardID=23&replyID=1986364&id=212807&skin=0

ciduo777 · 发表于 2007-4-21 16:36:00

谢谢ls

[求助]Prep-25

[求助]Prep-25

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