关于一道og中的题不明白,谁能帮忙解释一下

Matrixrl

1.  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

这题的acting as sentinels and to sound中的and是不是很奇怪啊,谁能解释一下,后面已经有个and了

干麻还加个and而且还要平行.

Matrixrl

up

krisliuyi

I think there are two parallelism: 1) such as defending ..., acting... and scouting ... 2) acting as ... and to ...

But if I were writing the sentence, I would prefer "acting as sentinels to sound a warning ...  "  Would appreciate it if anyone could further comment.   Thanks.

Matrixrl

解释是defending...acting and sounding...and scouting这样的并列，怎么看都不对呀

Matrixrl

没人帮忙回答一下吗?