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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。
1.虚拟语气，if句型里面不应该出现would，B错
而且撞地球这个事是假设的事，前后都是假设的情况，后面应该用could表示有可能
所以AE的strikes都错了，AD的can do也错了，ABDE错
2.代词指代错误，E的第二个it指代的是地球，这样句意错误E错，而且it多余了，that可以当代词指代主语
AB选项，and后面clause是完整句子，与"Scientists have identified an asteroid"平行，逻辑上不同
E选项，that后面不缺句子成分，但and that要与前面的定语从句平行，所以that也应该是引导定语从句，结构上有问题
D选项，but后面clause是完整句子，与"Scientists have identified an asteroid"平行，逻辑上不同
综上，算C选项
1） 看到and的时候要弄清楚what should be grouped.
A. (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 planet-wide destruction.)
B. Scientists have identified an asteroid, 2000 BF19, (that is about half a mile wide) and (that, if it were to strike Earth, could do xxxx)
2. if-then patterns
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从句用一般现在时，主句需用将来时，不能用could。”
“虚拟语气中的if从句不能用would”
“ 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）”
你这都哪里抄的乱七八糟的笔记？
1. 现在时，如果事情发生的概率很低，可以用could，可以在prep和og里找到大量的例子
2. 从句不用would用啥？
没有看到是引号吗！就是摘要老师的解析，帮助我自己记忆的考点！不喜欢也不要乱喷！谢谢
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if had done, would have done. if可以省略主语，但有条件，主语一致。
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。
有that就是identify两个递进的发现：an asteroid & 一个if句子
没有that就是an asteroid & 一个句子并列，这不可能
ac的时态用法都是对的
没有that 前面整句话和后面平行了，make no sense
注意并列句和定语从句在表意上的差别！！
错选A，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。
C是定语从句！！！
简单题！！！！
考察！
虚拟语气，没有明显的动词提示，这种假设的题一贯是虚拟语气，所以不要想歪了；
看到and，应该先确定它连接的两个部分是什么
根据句意可以知道，这个句子是在描述科学家发现的一个asteroid，所以and连接的两个部分应该是关于asteroid的两个事实，即an asteroid that...and that... 所以【half a mile wide】和【if it were to…】
⚠️and前面没有“，”说明and前后共用一个主语，所以不能加it
并列与修饰关系
A + B（定从修饰A）+ C
若C与B并列，则C逻辑上需修饰A
A + B（定从修饰A）；C
若C与A并列，则C逻辑上不能修饰A
1、A/B中“be...wide”与条件句是结构上和语义上都是不平行的。
2、C、D/E是双定语从句的平行，不能省略that.
3、C选项合理地使用了虚拟语气，“if sth. were to do sth, sth. would/could do sth”此结构是对将来的虚拟。
而且could与would平行。
4、D选项从句的主语改变为earth，逻辑意思改变。
5、E选项时态用错，应该改为“it it strikes...,it WILL...” ，定语从句必须要缺少某个成分
1、A/B中“be...wide”与条件句是结构上和语义上都是不平行的。
2、C、D/E是双定语从句的平行，不能省略that.
3、C选项合理地使用了虚拟语气，“if sth. were to do sth, sth. would/could do sth”此结构是对将来的虚拟。
而且could与would平行。
4、D选项从句的主语改变为earth，逻辑意思改变。
5、E选项时态用错，应该改为“it it strikes...,it WILL...” ，定语从句必须要缺少某个成分
虚拟语气： If alice ate pizza tomorrow，then she would become ill.（对未来不可能事件的虚拟）
hypothetical subjunctive + conditional（would could）
⑤Case That Never Happened（in the past）（对过去的虚拟--一件过去并没有发生）
If Sophie had eaten pizza yesterday，then she would have become ill.
IF PAST PERFECT,THEN CONDITIONAL PERFECT
A的真正错误是 //and前面没有逗号//，但and后面却跟了//句子it can do tremendous damage to part of the planet but ....。//
and如果前面没有逗号，后面必须和前半句共享主语。
DE错误。。。
虚拟语气 CE错误
D还存在一个问题：if Earth is struck by it 应该虚拟，一般现在表示恒定状态，在这道题里是不合适的
E it could experience a tremendous amount of damage， it多余了，另，主将从现
hen 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.
if do, then will do /can do
if did, then would do/could do
if had done, then would have done/could have done