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16. Less than 35 years after the release of African honeybees outside Sao Paulo, Brazil, their descendents, popular known as killer bees had migrated as far north as Southern Texas.
A. Less than 35 years after the release of African honeybees outside Sao Paulo, Brazil,
B. In less than 35 years since releasing African honeybees outside Sao Paulo, Brazil,
C. In less than the 35 years since African honeybees had been released outside Sao Paulo, Brazil,
D. It took less than 35 years from the release of African honeybees outside Sao Paulo, Brazil, when
E. It took less than 35 years after the time that African honeybees were released outside Sao Paulo, Brazil, and then

这个题目我主要想问的是时间的表示和动词时态的问题
BDE可以通过其他语法点排除掉，所以先不看了。答案是A

偶的具体问题：
1）未划线部分用的是过去完成时，如何理解这个时态？A选项如何提供的过去的时间点做参照的？C选项的过去完成时我也说不出所以然来...
2）in less than the 35 years since... 和 less than 35 years after 有什么区别？

以下是引用YY_lalala在2007-3-31 23:09:00的发言：

这个题目我主要想问的是时间的表示和动词时态的问题
BDE可以通过其他语法点排除掉，所以先不看了。答案是A

时间和时态算是我的薄弱环节，向大家请教～

时态也是我的死穴。但对于此题，正好我曾经和LZ有同样的疑问，幸运的是闹闹给了我很大帮助，在此与LZ分享：

1.画线后面之所以是过去完成时，因为前面“Less than 35 years after the release of African honeybees outside Sao Paulo”——以过去的某个动作开始(the release)持续了不到35年，注意，不是到现在；

2.关于C的错误，我和闹闹分析过很久，曾经认为since引导的时间状语从句中不能有完成时，后来发现此说法不成立。查到一个例子：...those 15,000 shares went up to more than $3 per share since he had first given me the tip.

所以，又查了些资料：解释为：要么"in 1980"，表过去时；要么"in+时间"，表将来时，例如in the future 在将来、in two weeks 在两周后。关于这点F大侠也曾提到。

至于A，大家都倒下了，只有它了。但什么介词都没有，我还是一直觉得很别扭。俺也期望，有一个大侠踩着七彩祥云，能过来给俺点拨一下啊...

1）honeybees was released 和 their descendants migrated to 是发生在两个不同时间点的动作，中间差了less than 35 years，但是C却对这两个动作用了同样的时态；A把第一个动作转化成了名词release，避免了两个动作时间时态上不consistent的问题

2）受tasteofbit启发，分别查了下in和since的含义，产生了这两个词用在一块会不会有问题的疑问
A，the release提供了一个时间点，less than 35 year after the release表示清楚了由这个点开始的一段时间。
C，since本身就强调是一段时间，朗文的解释：from a particular time or event in the past until the present, or in that period of time, 已经有在那段时间里面的含义了，再加in，构成redundant

问了一个老外，他认为过去完成时的表达中必须有明确的时间的提示。也就是说C中 since African honeybees had been released outside Sao Paulo中的had been来得莫名其妙。

BC中In...since结构错，B中since doing 错，D中It....,WHEN,改变原意和结构，错，E，the time when..

ONGMAN中关于SINCE的叙述：Use since to say that something started at a point in time in the past, and is still continuing : He has been living in Leeds since 1998. | We've known about it since May.
Since is usually followed by a time expression ('last year', 'this morning', '4 o'clock' etc) or by the simple past tense. Use the present perfect or the past perfect in the other clause : I have loved movies since I first went to the cinema. |He had been seriously ill since Christmas.

!! Speakers of British English usually say it is a long time/two weeks etc since ..., and speakers of American English it has been a long time/two weeks etc since ..., but both uses are correct : It's weeks (BrE)/It's been weeks (AmE) since I saw Grandma.

since的四种用法
	1) since +过去一个时间点　(如具体的年、月、日期、钟点、1980, last month, half past six)。　 I have been here since 1989. 　　 2) since +一段时间+ ago 　 I have been here since five months ago. 　 3) since +从句　　 Great changes have taken place since you left. 　 Considerable time has elapsed since we have been here. 　 4) It is +一段时间+ since从句　 It is two years since I became a postgraduate student.

A）35 years after the release of African honeybees, their descendants had migrated as far north as southern Texas.

c) In the 35 years since African honeybees had been released, their descendants had migrated as far north as southern Texas.

我觉得c的问题在于，35 years since+从句是不对的，我查到的since用法，无论是做Prep还是conj，表示“自xxxx之后”的动作/时间，都用的是句子，没有用时间短语的。用时间短语的话应该只能用after吧？

居然google到很多**years since+clause的用法。。。但是我想问formal的文体中可以这么用么？因为在字典当中没看到过。我怀疑这种用法是不是It has been **years since+clause的简写。。。

还请nn说说到底有没有时间短语+since的用法，如"In the 5 years since I last visited shanghai,...."

in本身已经有表示在...时间之内，所以in 和 less 合用就太啰嗦了

以下是引用tasteofbit在2007-4-2 2:38:00的发言：

以下是引用goyce36在2008/7/10 10:34:00的发言：
release是过去的时间点，那么after release，应该是过去的之后。而过去完成时是过去的之前。这怎么对呢？

这么老的贴，我又翻出来顶了~~我也很疑问C为什么不对~这个时态同问！