[求助]TT GWD-4-1????

Q1:

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

1. both
        dating
2. both
        of which have dated
3. and
        each has dated
4. and
        each one dating
5. each
        one of which date

  
Answer:A

...

弱弱地说：

这个算是effectiveness的问题 which指代不清晰 一般作为就近指代

如果用ing 对象优先考虑是主句主语

所以A>E

date用复数么有错

这题的正确答案A是不是both引导的独立主格？

既然each可以引起独立主格，both也应该可以吧？

查了很多独立主格的解释，没有相关的明确例子。。。请教！