prep语法中的一个困惑

西风瘦马

13.   (25151-!-item-!-188;#058&002234)

 

One of the earliest known birds with a beak and contour feathers, Confuciusornis sanctus, with large clawlike "thumbs" on its wings, which probably helped them to climb up to a launching position for flight.

 

(A) with large clawlike "thumbs" on its wings, which probably helped them to

(B) with large clawlike "thumbs" on their wings, which probably helped it to

(C) had large clawlike "thumbs" on its wings, which probably helped them

(D) had large clawlike "thumbs" on its wings, probably to help it

(E) had large clawlike "thumbs" on their wings, probably to help it

 

这题中probably to help it应该是作状语吧，那为什莫要加个逗号呢？不加可不可以呢，加与不加有区别吗？好像prep中很多作状语的都在前面加个逗号，对prep的这个独特的现象很困惑，请NN解惑，多谢

wnlovess

LZ, 请注意语法考察的关键是什么，不要想得太偏激：逻辑〉Agreement>arallesim>Idiom=Sentence structure

A/B：没有谓语，明显错误

CE：代词指代错误：明显错误：(C) had large clawlike "thumbs" on its wings, which probably helped them

                                                       

                                                        (E) had large clawlike "thumbs" on their wings, probably to help it

希望对你有帮助，不说了，我16号就考了，还要继续看啊。

加油

                                                        (E) had large clawlike "thumbs" on their wings, probably to help it

希望对你有帮助，不说了，我16号就考了，还要继续看啊。

加油