Tom's mother always makes him ______ for a long time. [ ]

A. to study

B. study

C. studying

D. studies

上述哪项是半夏厚朴汤和枳实薤白桂枝汤组成中均有的药物（）

A.半夏

B.瓜蒌

C.黄连

D.枳实

E.厚朴