Equipped with modern facilities, today' hospitals are quite different from _____ 
A. those of the past 

B. the past 

C. which of the past

D. these past

答案为 A，C 为什么不行？which 不能代替前面出现的词么？which 不能代替复数复? 谢谢!

【答】这里的 those 是替代词，those of the past = the hospitals of the past。

which 不能作替代词使用。