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题库 / Prep2008E1-SC-246
Scientists have identified an asteroid, 2000 BF19, that is about half a mile wide and, if it strikes Earth, it can do tremendous damage to part of the planet but probably not cause planetwide destruction.
and, if it strikes Earth, it can do tremendous damage to part of the planet but
and, if it would strike Earth, part of the planet could experience a tremendous amount of damage but it would
and that, if it were to strike Earth, could do tremendous damage to part of the planet but would
and that, if Earth is struck by it, can do part of the planet tremendous damage, but it would
and that, if it strikes Earth, it could experience a tremendous amount of damage but
题目分析：
本题涉及许多虚拟语气的相关概念。
选项分析：
A选项：由于并列连词and身后没有that，且 it can do tremendous damage to part of the planet是完整的不缺少任何成分的完整句（定语从句中必然缺少某个成分），所以本选项中具有并列关系的是Scientists have identified an asteroid, 2000 BF19和 it can do tremendous damage to part of the planet。在逻辑上，前者是表述发现行星的，后者是描述行星特点的，两者没有并列关系。
B选项：本选项错误同选项(A)。另外，虚拟语气中的if从句不能用would。
C选项：Correct. 本选项在语法和逻辑上均是正确的。
D选项：并列连词but身后的it would probably not cause planetwide destruction中是完整的句子，无法和定语从句并列，只能和主句Scientists have identified an asteroid, 2000 BF19并列。同(A)理，这种并列是不成立的。
E选项：并列连词and身后的it can do tremendous damage to part of the planet是完整的不缺少任何成分的完整句，并列关系错误同选项(A)。另外，if从句用一般现在时，主句需用将来时，不能用could。
AB：and表示并列无联系的事实，事实上两者都是科学家发现的关于行星的描述。
D：不平行。
E：错误使用一般现在时，一般现在时用来描述一个不变的现象。
似乎也没表达明白
if从句的时态要将所表述的与之相反的时态前推一个时态，主句的时态就是所表述的与之相反的时态
if do, then will do /can do
if did, then would do/could do
if had done, then would have done/could have done
if do, then will do /can do
if did, then would do/could do
if had done, then would have done/could have done
when you look at these sentences with "and", you need to figure out what should be grouped -- in other words, which ideas are meant to be expressed in parallel structure.
in this sentence, those two ideas are the two facts about the asteroid:
* the asteroid is about 1/2 mile wide.
* if the asteroid strikes earth, blah blah blah xxxxx will happen.
只要把并列判断出来，这个题就只能选C了。
第二个that后面是定语从句？这两个that是什么句子成分结构？
虚拟语气中的if从句不能用would, why???
小行星炸地球，虚拟语气迅速找到关键词were
感觉if引导的也可以是真实条件句。只要条件成立，结果也可成立。选项C中用虚拟语气，用were表示和真实情况相反或不可能发生，如果曾经撞过，可以有相反的状况----如果不撞击的话，会.....。如果反过来，感觉逻辑上不通。而且文章没有给出信息说不可能发生。
选项A的情况and也可以实现并列。比如：I found a garden, and it is beautiful. and表示顺承上句，进一步解释。
请老师指正。
解释已经写的非常清楚了。and是并列连词，连接两者必须在逻辑上对等。你给出的这个例句，应该改成：
I found a beautiful garden.
或者换成非限制性定语从句也许也可以。
你说的是对的， 别听那老师瞎说，A就是and前少了个逗号所以不对
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