请教run-on错误的区分

96. (29707-!-item-!-188;#058&003977)
In some species of cricket, the number of chirps per minute used by the male for attracting females
rise and fall in accordance with the surrounding temperature, and they can in fact serve as an
approximate thermometer.
(A) for attracting females rise and fall in accordance with the surrounding temperature, and they can
in fact serve
(B) for attracting females rises and falls in accordance with the surrounding temperature, which can
in fact serve
(C) in attracting females rise and fall in accordance with the surrounding temperature, in fact
possibly serving
(D) to attract females rises and falls in accordance with the surrounding temperature, and it can in
fact serve
(E) to attract females rises and falls in accordance with the surrounding temperature, in fact
possibly serving

这一题中的and后面有了个it不构成run-on错误嘛？但是我看有的题目在一个连词，比如but加上it 指代前句中的主语，就会构成run-on错误。这里为什么不会呢？我似乎在prep笔记里也看到说如果and连接2个句子，中间没有逗号就可以公用一个主语，如果两个句子有不同的主语，就必须有逗号在and前面隔开，这是不是run-on错误？请问该如何区分？

中间有逗号，前后句子是同一个主语也是可以的，只要前后的动作没有逻辑关系，不算run-on，也不算累赘。

比如在此：rise and fall和serve不是同时发生的动作, 不存在逻辑关系。如若存在逻辑关系应该是累赘吧，不过GMAT里面不会把这个作为考点。