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题库 / Prep2008E1-SC-239
Were it not for the fusion-powered heat and radiation that rush from its core, instead its own weight would cause a star to collapse.
instead its own weight would cause a star to collapse
instead a star would have collapsed under its own weight
a star would have to be collapsing under its own weight
a star would collapse under its own weight
its own weight would have caused a star's collapse
题目分析：
略。
选项分析：
A选项：语法有误，虚拟语气句子，主句必须一开头就是主语，而不能是连词、副词，因此instead错误。
B选项：instead错误同选项(A)。
C选项：would have to be collapsing是很混乱的时态；would have to是不很肯定的语气，其表达的是have to do的内容只是一个假设，并不是真的“必须”，而have to表达的意思是，要做的事情非常重要，“必须”去做，前后矛盾。
D选项：Correct. 本选项在语法和逻辑上均是正确的。
E选项：名词短语a star’s collapse需改为不定式短语a star to collapse，这点考查了不定式和名词的区别，用之于本题，显然地，cause的约束力较强，身后应用不定式做宾语和宾语的补足语。
虚拟条件句的四种形式：
But for N, S + should/would/cold/might + V / (have Vpp.) 若不是N, S应该….
= If it were not / (had not been) for N
= Were it not for N / (Had it not been for N)
= Without N（介词只有without可表虚拟语气）
虚拟语气的时态：
时间 从句谓语形式 主句谓语形式
将来 动词过去式(be用were)
should + 动词原形
were to + 动词原形 would / should / might / could + 动词原形
现在 动词过去式(be 用 were) would / should / might / could + 动词原形
过去 had +动词过去分词 would / should / might / could have + 动词过去分词
RON： AB的真正错误是if it were not和instead之间的重复
虚拟语气的四种形式：
1. But for N，S +should/could/would+v-----若不是N，S应该
2.If it were not for N
3.Were it not for N
4.Without N
未划线部分的it指代后面句子的主语
Were it not for意思是：如果不是的话，和instead意思重复了。所以A,B错误。同时需要注意的是前半句用到了代词it和its，所以后半句需要明确指出代词指代对象，通过代词its core这里就可以判断出its指代的是star。最后，would do 和would have done的区别在于，would do是指将来，would have done是指过去应该做什么，完全不同。
虚拟语气的四种形式：
1. But for N，S +should/could/would+v-----若不是N，S应该
2.If it were not for N
3.Were it not for N
4.Without N
未划线部分的it指代后面句子的主语
对啦，todo和动词，虚拟语气