求助11th黄皮OG59这道题

His studies of ice-polished rocks in his Alpine homeland, far outside the range of present-day glaciers, led Louis Agassiz in

1837 to propose the concept of an age in which great ice sheets had
    existed in now currently temperate areas.

(A)            in which great ice sheets had existed in now currently temperate areas

(B)           in which great ice sheets existed in what are now temperate areas

(C)           when great ice sheets existed where there were areas now temperate

(D)           when great ice sheets had existed in current temperate areas

(E)           when great ice sheets existed in areas now that are temperate

正确答案是b，只是不明白为什么exist不能用过去完成时，难道这道题这里不应该用过去完成时表示过去发生结束的事情吗？不懂……

不对吧，这到题的正确答案是B啊，不是E，但对于B我不明白，还请楼下的NN解答，感谢感谢～

谢谢楼上的细心呀！我马虎了，呵呵

B中为什么用what are now temperate areas这玩意,好象没有见过这种表达的,哪位能帮忙举几个例子,WHAT 搞得怪怪的,

直接用B选项改成这样,in which great ice sheets existed in now temperate areas,是否正确,简洁呢?

请NN指教

Anybody here?

我是觉得一般只有人的动作才会用上过去完成时。

我也没见过What is or are now的用法。

在网上搜了搜，发现有个关于What用法的总结，很不错：

http://www.newstarnet.com/phpcode/web/view_detail.php?news_art_id=13300

What作为缩合连接代词
        (newstarnet.com)
(newstarnet.com)
例句1：The chief foods eaten in any country depend largely on ____ best in its climate and soil. (A)it grows (B)what grows (C)does it grow (D)what does it grow 答案B (newstarnet.com)
例句2：During the eighteenth century, Little Turtle was chief of the Miami tribe whose territory became ____is now Indiana and Ohio. (A)there (B)where (C)that (D)what 答案 D (newstarnet.com)
(newstarnet.com)
1.What之所以被称为缩合连接代词，因为它是先行词与关系代词的复合体，即what=all that=the things that。在上述等价关系中，all或things均为不定代词，其指代的名词由句意决定，如：在例1中what=the crop that，在例2中what=the place that。 (newstarnet.com)
(newstarnet.com)
2.由于what由两个词构成，所以what在前后句即主从句中必须同时都作成分，即必须作两个成分。如： 在例1中，what既是介词on的宾语，同时又是动词grows的主语。 (newstarnet.com)
(newstarnet.com)
3.what引导的句子相当于一个名词，可以自由地作主语，宾语和表语。换句话说，what可以引导主语从句，宾语从句和表语从句。 (newstarnet.com)
(newstarnet.com)
4.在考试中，n+what通常错，因为what前不需要先行词。再者，n+what=n+the things+that显然，n和things间无法连接。 (newstarnet.com)
(newstarnet.com)
5.在考试中，prep+what+SVO通常错，而且应该改为：prep+which+SVO。因为what可以作介词的宾语，但是在完整的从句SVO中无法作成分。 (newstarnet.com)
(newstarnet.com)
6.what is now作为一个可有可无的短语，在考试中通常是正确答案。 (newstarnet.com)
例如，在例2中去掉" what is now"也不会影响句子结构。 (newstarnet.com)
(newstarnet.com)
What作为关系形容词
        (newstarnet.com)
(newstarnet.com)
What作关系形容词时，其结构为"What+名词"，其含义为"所有的…"，"尽可能多的…." 如：I will give you what help I can. 我会给你尽可能多的帮助。实际上，此时What=all…that…；所以，在考试中，有以下两个特殊结构出现：What little=the little … that；what few=the few … that (newstarnet.com)
(newstarnet.com)
What作为关系副词，引导感叹句。主要有以下三种句式 (newstarnet.com)
1.What+a/an+形容词+单数可数名词+(主谓部分)！其中主谓部分可以省略。如： What a lovely girl she is! (newstarnet.com)
(newstarnet.com)
2.What+形容词+不可数名词或复数可数名词+(主谓部分)！如：What good books you are reading! (newstarnet.com)
(newstarnet.com)
3.What+a/an+单数可数名词 ！此结构中，名词分为两类，一类是没有感情色彩的普通名词，一类是具有感情色彩的名词。如：What a night! 可以是褒义，也可是贬义。What a mess! 只能是贬义，直接译为"多么乱啊！" (newstarnet.com)
(newstarnet.com)
必须掌握的What的其他重要知识点
        (newstarnet.com)
(newstarnet.com)
1. What 既可以指人，也可以指物，如： Most of what archeologists know about prehistoric cultures is based on studies of material remains. 在上句中, What = the knowledge that 再如：In her time, Isadora Duncan was what we would call a liberated woman. 在此句中, What=the person that。 (newstarnet.com)
(newstarnet.com)
2. What 还可作形容词，意为"什么"，如：Children instinctively know what foods are good for them. (newstarnet.com)
(newstarnet.com)
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