Verbal Review 2nd SC 第2题 麻烦大神们帮忙解释一下

catty2004

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

a) acting as senitels and to sound
b) acting as senitels and sounding
c) to act as senitels and sound
d) to act as senitels and to sound
e) to act as senitel sounding


我的理解是 "act as sentinels and sound warning" are ways to defend the entrance， not as separate duties i.e.

...different duties such as
                           1) defending the entrance:
                                         a)to act as sentinels
                                         and
                                         b)sound a warning ...
                           and
                           2) scouting outside....

吴下锕蒙

照楼主的理解，我抛出两个问题
1. to act as senitels and sound 前面为何加逗号？
2. C可以，D为何不可以？

catty2004

吴下锕蒙 发表于 2013-8-11 08:10
照楼主的理解，我抛出两个问题
1. to act as senitels and sound 前面为何加逗号？
2. C可以，D为何不可以 ...

高见！果真一针见血！！　

heehee, 其实原本认为D不parallel, since to act as NOT same as to sound, 现在看来　act and sound both verb and "to" is implied.....

sarahzzz

吴下锕蒙 发表于 2013-8-11 08:10
照楼主的理解，我抛出两个问题
1. to act as senitels and sound 前面为何加逗号？
2. C可以，D为何不可以 ...

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. 请问这里acting 和 sounding 是不是一个小平行，depending，acting，and scouting是大平行？