JJ里一个完整题目，请指教

Avantasia

The Acoma and Hopi are probably the two oldest surviving Pueblo communities, both dating back at least a thousand years.

A. both dating

B. both of which have dated

C. and each has dated

D. and each one dating

E. each one of which date

牛人的参考答案是A，但是both dating这里做什么成份？有点独立主格的感觉，但是both好像没听过可以引导独立主格，做定语又没看过这么代词单独放在句尾的。我倾向选B，不知道大家意见如何？

Avantasia

补充一个大全上面有点类似感觉的题目：

1.        India is country with at least fifty major regional languages, of whom fourteen have official recognition.

(A) of whom fourteen have official recognition

(B) fourteen that have official recognition

(C) fourteen of which are officially recognized

(D) fourteen that are officially recognized（C）

(E) among whom fourteen have official recognition

三脚猫

有个疑问date back 用完成时恰当吗?

Ａ可以理解为的both( communities）

Avantasia

我再想想。。。

Avantasia

犯晕了，感谢！

z520m

both of which这个which指代有问题，可以认为指代communities,并且这个have dated很有问题，date back是追束到的意思，应该用一般现在时态后一般过去时态，不管如何也不可能用完成时态，在og中明确说明，没有明确时态标志不能用完成时，所以B错。