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题库 / Prep2012-SC-39
In his experiments with gravity, Isaac Newton showed how the motion of each planet in the solar system results from the combined gravitational pull of the Sun and of all the other planets, each contributing according to their mass and distance from the others.
of all the other planets, each contributing according to their
of all the other planets, with each of them contributing according to their
all the other planets, each of which contributing according to its
all the other planets, each contributing according to its
all the other planets, each of which contribute according to their
题目分析：
不同选项mass的所有者不同，在(A)(B)(E)中，mass的所有者是their；在(C)(D)中，mass的所有者是its。请注意，all the other planets身前是否加of对于本题影响不大，加上或者不加均可。
选项分析：
A选项：each contributing according to their需改为 each contributing according to its。代词each是单数，their的指代对象是all the other planets，每一个行星只能由于自己的质量（mass）和距离（distance）决定，不能说是由于所有其他行星的质量和距离决定。
B选项：their应改为its错误同选项(A)。
C选项：each of which contributing according to its mass and distance from the others是非限定性定语从句，其中缺少谓语动词。
D选项：Correct. 本选项在语法和逻辑上均是正确的。
E选项：their应改为its错误同选项(A)；定语从句中的谓语动词contribute主谓一致有误。
D. all the other planets, each 【contributing √】 according to its
Correct use of 'each of which' -
select any two answer choices, each of which can be used to complete the sentence.
I have bought several books, each of which is based on a different theme.
考察：
单复数，独立主格，非限制性定语从句
前： of all the other planets和“all the other planets” 都是可选的，不用过度纠结这里。这也是gmac设置的拖延时间的陷阱。
中后：
1.each后面跟its，排除abe。
2.which非限制性定语从句和独立主格的区分
非限制性定语从句中有which（which引导定语从句）：all the other planets, each of which contributing according to its；->但是需要注意的是从句必须是一个句子要有自己的谓语，而这里用了contributing导致没有谓语，不成句。
独立主格： all the other planets, each contributing according to its->后面独立主格省略了谓语is，正确，each是独立主格的主语，后面加ing或者过去分词都可以构成独立主格； 作状语修饰主句，表示对主句的补充说明。
each 是同位语或独立主格，可以修饰整个句子：移动起源于拉力。如何起源，每个星体通过各自的体积和距离来影响拉力的大小。
或作限定词，which apple do you like？
We redoubled our efforts, each man working like two.
代词不能引导独立主格，因为代词指代先行词本身。
如：We redoubled our efforts, each man working like two. 我们加倍努力，一个人干两个人的活。
D这里的each contributing according to its mass and distance from the others作独立主格，在补充说明pull是如何产生motion的。
4D)each作为独立主格的主语
this doesn't happen in choice (c); there is no verb present in the modifier.
d后是独立主格