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OG178. In the last few years, the number of convicted criminals given community service sentences. which allow the criminals to remain unconfined while they perform specific jobs benefiting the public, have risen dramatically.

(A)  sentences, which allow the criminals to remain unconfined while they perform specific jobs benefiting the public, have

(B)  sentences, performing specific jobs that
   benefit the public while being allowed to remain unconfined, have

(C)  sentences, performing specific jobs beneficial to the public while they are allowed to remain unconfined, have

(D)  sentences which allow them to remain
   unconfined in their performing of specific
   jobs beneficial to the public has

(E)   sentences allowing them to remain
   unconfined while performing specific jobs
   that benefit the public has

答案为E，问题是while permforming 为何要省略逻辑主语？难道不会引起和allowing 是同一逻辑主语的逻辑歧义？

请帮忙解释。谢谢！

请英雄指点！！！

形式：
a) 正确形式:
表示时间/条件/转折/让步的连词(when/while/if/unless/although/even though/even if) + 形容词短语/-ing短语/-ed短语
(逻辑主语等于句子主语)  (所以when a child/ when children是错的； if + n.也是错的)
b) 错误形式:表示时间/条件/转折的连词 + 介词短语/名词短语 (although just inside the orbit of Jupiter是错的)
c) 特殊情况nce可以加介词短语/名词短语; whatever可以加名词短语

条件：
第一点是毫无疑问的：逻辑主语等于句子主语
第二点也是必须的：从句的谓语必需是be（没要求主句谓语也必需是be！，换句话说可以看成是省略了一个be），且从句主语和谓语要么同省，要么同留。

LZ其实这个题，即使在while之后补出了they也是很别扭的。

In the last few years, the number of convicted criminals given community service sentences， which allow the criminals to remain unconfined while they perform specific jobs benefiting the public, have risen dramatically.

这道题目的while结构首先是用来修饰定语从句的。因为while之前没有COMMA.

我们在阅读一个句子的时候，碰到代词，人脑习惯上把它和语法上平行的名词对应起来。比如从句S-主句S, 从句V-主句V, 从句O-主句O.

你看如果在while结构后+they,我们也会很自然的把它和which（sentence)对应起来，而且它们语法上还是符合agreement的。

但是，经过逻辑分析我们发现they指代的是criminals. 于是当这种平行被破坏了，所以A读起来非常非常别扭。

参考这两句话。Ronpurewal-Manhattan Gmat

(1) although the freshmen beat the varsity team in the opening exhibition games, it has not lost a game since.
    
(2) although the varsity team lost the opening exhibition games to the freshmen, it has not lost a game since.

  in both of these examples, 'it' is completely unambiguous: it must refer to 'varsity team'. however, #1 is much, much harder to read, because 'they' is not grammatically parallel to its antecedent (the pronoun is the subject of the second clause, while the antecedent is the OBJECT of the first clause). #2 is natural, because both the pronoun and the antecedent are the subjects of their respective clauses.

所以我猜测，当while引导从句中主语位置上是 代词 的时候，代词如果和主句的主语在逻辑上不够成一致，那么就是一个不受欢迎或者，awkward的表达结构。

而如果仅以 while+分词 出现，避免代词出现，那么人脑就不会那么难以接受。所以E中省略了代词。

浅见，open to be discuss.

所以我猜测，当while引导从句中主语位置上是 代词 的时候，代词如果和主句的主语在逻辑上不够成一致，那么就是一个不受欢迎或者，awkward的表达结构。

而如果仅以 while+分词 出现，避免代词出现，那么人脑就不会那么难以接受。所以E中省略了代词。