帮忙看一下，谢谢

jbc88

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


OA：b。

答案没问题 。doing ,doing and doing.
但后面还有个and scouting 呢？这句结构岂不成doing ,doing and doing  and doing？ 这种结构对吗？

jiaoqi

这是把acting和sounding看做一类职责，作为守卫并在危险到来时示警，acting和sounding构成一个小的并列，同时他们和其他的doing构成一个大的并列。还有就是第一个and前面没有逗号，如果有两个以上的n并列，最后一个的and前面要有逗号

mongmong

http://gmatclub.com/forum/sounding-87460.html


Oh ! I get it now ..........!!!!!!


Sorry for the third consecutive post though !!!!

Actually, even though logically, a sentence should be in the format
A,B,C, D & E
[where A= defending
B = acting
C = Sounding
D = Scouting
& E = Roosting !!]

However, this is an exception.

If u look at the sentence, they have already mentioned D & E as "and scouting" & "and roosting" in the NON_UNDERLINED part. So taking the GMAC to be right(!), we can parallel this structure!

So in order to parallel that we can have "acting as sentinels" and "sounding" separated by an "AND"

Hope i have made things clearer and not confused u all further ..!!!

sunnyybao

感谢楼上提供的链接，可是对于这个问题我依旧困惑~
roosting 在这里不是与scouting 并列的吧？我觉得这里是修饰sites的吧？
scouting outside the cave for new food and roosting sites.

mongmong

感谢楼上提供的链接，可是对于这个问题我依旧困惑~
roosting 在这里不是与scouting 并列的吧？我觉得这里是修饰sites的吧？
scouting outside the cave for new food and roosting sites.

-- by 会员 sunnyybao (2011/5/20 14:11:25)

嗯，我同意，roosting 因该是修饰sites的,而不是动词形式

mongmong

那我还是不懂ＯＧ为啥解释说四个动词是并列，应该是A and B, A=defending, B= scouting, 而acting and sounding来修饰A的？

ivydorian

这种结构再正常不过了 哈哈

mongmong

这种结构再正常不过了 哈哈

-- by 会员 ivydorian (2011/5/23 15:37:25)

能说得详细点吗？