OG 3 Choice E 解释

3.       Some bat caves, like honeybee hives, have residents that take on different duties such as defending the entrance, acting as sentinels and to sound a warning at the approach of danger, and scouting outside the cave for new food and roosting sites.

(A)  acting as sentinels and to sound

(B)  acting as sentinels and sounding

(C)  to act as sentinels and sound

(D)  to act as sentinels and to sound

(E)   to act as a sentinel sounding

Because the verb phrases used to describe the bats' duties are governed by the phrase different duties such as, they should each be expressed in the present participial (or "-ing") form to parallel defending and scouting. Choices A, C, D, and E all violate parallelism by employing infinitives (to...) in place of participial phrases. In E the singular sentinel is not consistent with residents，and the omission of and distorts the meaning of the original. Only B, the best answer, preserves the sense of the original, uses the correct idiom, and observes the parallel­ism required among and within the three main verb phrases.

作对了，在对E项的解释方面请大家帮我理解，谢谢

原文, acting as sentinels and sounding, 两个动作.

E, sentinel sounding a warning at the approach of danger,  sounding修饰sentinel, 意思改变.

正有疑问，多谢。

defending..., acting...and sounding..., and scouting...

为什么要两个and？多别扭啊！

OG解释的最后一句说得清楚：the parallelism required among and within the three main verb phrases. acting和sounding是一个概念的两个范畴，可以理解为：作为巡逻兵，也就是监听危险的警报。

这是rt316说的，我觉得很对！

我觉得第一个and 用途和第二个不一样，第一个只是acting 与sounding的并列；然后才是A，B ，and C吧。

同意~~

思维开阔了。谢谢。

先是A ..., B ... , and C...的并列，然后 B 里面其实还有个小并列，分为 B1 ... and B2 ... 这就是为什么有两个 and 的原因了