[求助]OG 3 ， and到底怎么用

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

答案是B没错。可是哪位NN能和我说一下，这个句子中的并列短语啥关系啊。怎么and可以用这么多，不是说and只是在并列成分的最后一个前用么？我印象中的~~

如果B对的话，那and的用法我就糊涂了

请大侠指点，谢谢。

a，（b and c），and d

中间括号里面的是一个整体概念

thx!

我真是菜啊