OG11-75的疑问：为什么能省掉did

fuziyang

Salt deposits and moisture threaten to destroy the Mohenjo-Daro excavation in Pakistan, the site of an ancient civilization ____________ in the Nile delta and the river valleys of the Tigris and Euphrates.
A. that flourished at the same time as the civilizations
B. that had flourished at the same time as had the civilizations
C. that flourished at the same time those had
D. flourishing at the same time as those did
E. flourishing at the same time as those were
答案是A

整个句子，我觉得用从句的话，应该为
the site of an ancient civilization that flourished at the same time as the civilizations in the Nile delta and the river valleys of the Tigris and Euphrates DID.
如果不用从句，应该为
the site of an ancient civilization flourishing at the same time as those in the Nile delta and the river valleys of the Tigris and Euphrates. （另外，这里those是不是有指代不明之嫌？）

为什么A的did可以省略？还请牛牛们指点！多谢了！

doudoulong1302

记得好像有人说过指代对象很明确的时候就不必补出动词了，CD上有这道题讨论的，你可以找找看

andreasyang

举个例子
i run as fast as Tom 没错吧，很明了吧
所以就不用
i run as fast as tom does，does完全可以省略的