GWD-12-Q3:
Were itnot for the fusion-powered heat and radiation that rush from its core, insteadits own weight would cause a star to collapse.
A. instead its own weight would cause a star tocollapse
B. instead a star would have collapsed underits own weight
C. a star would have to be collapsing under itsown weight
D. a star would collapse under its own weight
E. its own weight would have caused a star’scollapse
答案是D没有问题，可是我不太清楚C中的would have to be怎么错了，prep的解释如下：
A. 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 作者: zhengqingku 时间: 2011-11-25 21:04
其次，have to 的意思，在原文要表达的意思里，不存在。Have to 不代表一个“结果”，而倾向于“为达某目的而必须采取的措施”
example:
were it not for the abundant jj, the average gmat score of the chinese test takers would be lower (as a result).
were it not for the abundant jj, i would have to spend 20 seconds more on every gmat question (in order to understand the questions).
明白否？作者: honoluluhono 时间: 2011-11-26 06:30
明白了，哈哈。谢谢！作者: Amy1989618 时间: 2011-11-27 21:37
同意二楼！
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.
A. instead its own weight would cause a star to collapse
B. instead a star would have collapsed under its own weight
C. a star would have to be collapsing under its own weight
D. a star would collapse under its own weight
E. its own weight would have caused a star’s collapse
再举两个例子：
I didn't go to work; instead, I went to see my parents.
to go to work, 和 to see my parents, 构成对比。两个分句没有反对关系，反对的是连个动词结构
I ordered tea, but the waiter gave me coffee instead
两个分句的相反通过but来体现，instead 强调 tea和coffee的相反
排除A B
E项，主句使用了would have, 该虚拟表示和现在目前的状况相反的，依据规则，条件状语从句应该使用 if ...had not been/been for...的结构，因为该假设条件的必须是与过去的事实相反，才能导致主句中虚拟情况和现在完成的事实相反的情况。所以主句和从句时态不匹配。
其实不需要强调规则，只需要认识到：E项的虚拟是和现在事实的相反，也就暗示了这样一个事实：这个恒星还旧没有坍塌
但是作者想要表达的是客观事实，科学真理，谈论的是一般情况的恒星，不是在谈论仍没有坍塌的恒星。
举个例子:
If it had not been for the cancer , Steve Jobs would have see the publication of his biography
即使不是因为癌症，乔布斯会看到自己传记的出版。
这里主句中的would have表示与目前事实的相反，条件句中had been表示与过去事实的相反。
