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. (B) acting as sentinels and sounding (E) to act as a sentinel sounding
I wondered if we put answer B back to the sentence, the whole sentence will be " Some bat caves, like honeybee hives, have residents that take on different duties such as defending the entrance, acting as sentinels and sounding a warning at the approach of danger, and scouting outside the cave for new food and roosting sites" there are two " and " , it looks like uncomfortable, while I think answer E looks more plausible, " to act as a sentinel " modify sounding,please help me to explain it.
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The option B is correct because bat caves have 2 duties:
1)Defending the Entrance
2)Scouting outside the cave for new food and roosting sites.
Acting as sentinels and sounding a warning is how the bat caves are defending.It is not the part of the duties performed by the bats. Its an additional information provided via usage of comma of how bats defend the entrance. Even if you remove that part of the sentence the whole sentence structure will still make sense.And the option B is right because it maintains the parallelism in that structure using the words 'acting' and 'sounding'
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发表于 2004-1-8 02:22:00
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