Equipped with modern facilities,today's libraries differ greatly from_A those of the past Bthe past Cwhich of the pastDthese past 为什么C不可以

问题描述:

Equipped with modern facilities,today's libraries differ greatly from_
A those of the past Bthe past Cwhich of the pastDthese past
为什么C不可以

如果选C的话,缺先行词.