OG12 SC85 had,were,did 求解释

贤永恒

85. Salt deposits andmoisture threaten to destroy the Mohenjo-Daroexcavation  in Pakistan,the site of an  ancient civilization  
that ?ourished at thesame time as the civilizations in the Nile Delta and  the river valleys of the Tigris and Euphrates.

(A) that ?urished at the sametime as the civilizations

(B) that had ?ourished at the sametime as had the civilizations

(C) that ?ourished at the sametime those had

(D) ?ourishing at thesame time as those did

(E) ?ourishing at thesame time as those were

根据OG的解释，C,D中did,were是awkeard and unnecessary     但是，C中had则解释说是the wrong verb tense
为什么呢，求解释啊！！！

zzz0961

首先，这道题的比较不涉及助动词补出问题，所以补出的助动词是多余的。其次，这道题要求一般过去时，所以had错。

贤永恒

沉了，怎么沉了
             up！！！