My English-Chinese dictionary has disappeared. Who _____ have taken it? [ ]

A. should

B. must

C. could

D. would

古典学派的货币需求理论中最著名的有（）。

A.费雪的现金交易数量说

B.剑桥学派的现金余额说

C.凯恩斯的货币需求说

D.马克思的货币必量要论