关于who的指代问题求解

lainemai

TheKwakiutl recognized one social unit larger than the tribe--the confederacy（联盟）, which was a cluster of loosely knit, informally relatedneighboring tribes who interacted with themselves more often than betweenother tribes.

A tribeswho interacted with themselves more often than between

B tribeswho interacted among each other more often than among

C tribeswho interacted with one another more often than with

D tribes,interacting among each other more often than between

E tribes,interacting among one another more often than with

这道题的正确答案是C，但是以我当时的判断，因为想到manhattan语法里有这样一句话The pronoun who and whom must modify people.所以我直接就排除了带有who的选项，因为前面是tribes.哪位牛牛能帮我解答一下为什么呢~~谢谢~~