关于GWD1-Q30

GWD1-Q30:

The ancient Anasazi harvested such native desert vegetation as the purple-flowered bee plant, what they now commonly call wild spinach in northern Arizona and other parts of the southwestern United States.

A.      what they now commonly call

B.       a plant that they now commonly call

C.      now commonly called

D.      and is mow commonly called

E.       which it is now commonly called

 答案是c，但感觉c有点ambiguous. 不知是指the ancient Anasazi还是the purple-flowered bee plant.

这道题我也错了 貌似很少人错嘛。。。

A：成分缺少

B：不是Plant 被call

D ;and多余。

E ,whih it is..it错误，which指代错误

B错误在they指代的是The ancient Anasazi ,古人怎么能现在call呢 逻辑错误

同问：E选项是因为什么错？

1)是因为",+which"这种结构么？好像现在的考试已经不固定“逗号+which”必错了。

2) 是因为it is 没有省略么？对不起，这个问题有点蠢，which it is的结构本身就是错误的，请忽略这个点。

有点不解，请NN指教。本题最主要的是which is的省略，我想请问的是遇到这种情况,which is是必须省略，还是可省可不省？

谢谢！