OG12-SC-100 求赐教~

lovesiqi4665

The stars, some of them at tremendous speeds, are in
motion just as the planets are, yet being so far away
from Earth that their apparent positions in the sky do
not change enough for their movement to be observed
during a single human lifetime.
(A) The stars, some of them at tremendous speeds,
are in motion just as the planets are, yet being
(B) Like the planets, the stars are in motion, some
of them at tremendous speeds, but they are
(C) Although like the planets the stars are in motion,
some of them at tremendous speeds, yet
(D) As the planets, the stars are in motion, some of
them at tremendous speeds, but they are
(E) The stars are in motion like the planets, some of
which at tremendous speeds are in motion but


本题的答案是B，OG中对A选项的修饰部分的解释是"Placements of the modifying phrase and the comparison are awkward and ineffective"，从语法上说"The stars, some of them at tremendous speeds, are in motion just as the planets are..."应该是没有错误的对吗？
还有就是请教一下可以做修饰成分的句子结构，以前总是记着“介词短语”“分词结构”可以做修饰短语出现在句子中，并且常常在修饰句子前和后用逗号隔离出来，在本题中有一个”some of them at tremendous speeds“的修饰成分，请问这是什么修饰成分呢？为什么也可以隔离出来作为修饰短语出现呢？问题比较低级，还请NN多多提点呀，真心感谢~！

ozymendias

同问以上问题，能不能改成some of which are ..阿？不用some of them ?

sylivayjer

SOME OF THEM 是同位语，
A的错误原因在于，JUST AS 做比较，一般在句首，这样比较清晰。

lovesiqi4665

真心感谢解答！
就是说“some of them at tremendous speeds”在这里是同位语，拿正确的B答案来说，这个同位语是修饰名词“star”的对吗？以前看过很多句子，大都是同位语的先行词（通常是名词）后直接就跟着此名词的同位语修饰部分，B选项是一个完整的句子“the stars are in motion”之后才出现同位语，所以自己做题的时候都没有看出来,唉...

WesternCder

不是同位语. 同位语在逻辑含义上是可以互换的. 这里的some of 决定了不能互换, 因为范围不对.

这里是独立主格. 我手边没有语法书的电子版，从baidu上找了一个说明：

“独立主格结构”是由名词或代词作为逻辑主语，加上分词、形容词、副词、动词不定式或介词短语作为逻辑谓语构成。这种结构在形式上与主句没有关系，通常称为“独立主格结构”。

顺便给个简单例句。 He stood there, hands waving.

kobemvp

可是没有出现动词的现在分词 怎么构成的独立主格呢??

sjmdlycs

同问，B中的some of them里的them怎么不会指代不清？既可以指planets也可以指stars吧？还是因为其他选项都有明显错误，GMAT就让这个指代不清勉强通过？

bobochener

1，其他选项有明显的语法错误。GMAT要求Grammar>meaning>concise.
2, them/they/it优先指代主句主语。