一道OG，一道补充材料语法？

lyricling

OG136. Although schistosomiasis is not often fatal, it is so debilitating that it has become an economic drain on many developing countries.
(A)it is so debilitating that it has become an economic
(C)so debilitating is it as to become an economic

OG看不明白。C为什么不对？这里是单一主谓结构，可以用it is so debilitating as to become an economic　这样的结构，C项是不是将其倒装了？如果是这样，C项岂不比A更简洁？

补262.
Sunspots, vortices of gas associated with strong electro-magnetic activity, are visible as dark spots on the surface of the Sun but have never been sighted on the Sun’s poles or equator.
(A) are visible as dark spots on the surface of the Sun but have never been sighted on
(B) are visible as dark spots that never have been sighted on the surface of the
(C) appear on the surface of the Sun as dark spots although never sighted at
(D) appear as dark spots on the surface of the Sun, although never having been sighted at
(E) appear as dark spots on the Sun’s surface, which have never been sighted on

如果我区分不出来介词at 或on的不同，这道题该如何做

1stzhang

1、原来在一个帖子里讨论的相当详细。

2、这个题目如果不知道介词的区别还真的不好做

lyricling

第一题：能告诉我怎样找到那个帖子吗？我刚来不久，好多好的讨论都没遇上。
非常感谢！

第二题：那怎么办呢？哪位大牛能给点建议？

siebel

136 众说纷纭。我就是把它给记住了。
262 我还真不知道at和on有什么不同;-)
are visible ... as unidiomatic。
DE 用完成时无厘头。

lyricling

请问第二题，
为什么are visible不合语法？
为什么不能用完成时？完成时可以表示从过去至今从来没有被看到呀？

[此贴子已经被作者于2003-5-29 21:06:05编辑过]

1stzhang

so debilitating is it as to become an economic

是错误的，so ...as to 的so后面只能接adj/adv，不能接句子。如果把C改为it is so debilitating as to become an economic.在和A的比较中，它也是不好的，因为C没有反映
become这个动作的时态，换成你的话从逻辑意思上说，A在更加合理。

简洁原则必须在逻辑意思完全合理的情况下才可以使用，但是A/C之间有动词时态的差异。说明逻辑意思是不一样的，如果单从简洁入手，可能会错误

lyricling

再请教一下第一题，像become这种词用完成时态和用一般现在时有什么不同？难道这里不是讲一个客观真理吗？不应该用一般现在时吗？

1stzhang

当然不同，一个是成为，一个是已经成为，完成时态的动作是已经发生了。

She becomes my wife./She has become my wife. 当然成为我的wife是客观事实，但是这两个句子是有区别的。

这个题目主要还是so ...as to 的so后面只能接adj/adv，不能接句子。

lyricling

请请教？
这个题目主要还是so ...as to 的so后面只能接adj/adv，不能接句子。

可我觉得这是一个So提前的倒装句呀？so 后并没有接句子呀。so debilitating is it as to become an economic，可不可以看成是it is so debilitating as to become an economic的倒装呢？多谢！

1stzhang

so...as to的用法十分死板，就是要使to后面的动词的发起明确而合理，它只用于简单的结构中。so....as to的倒装没有见到过。