若3amb5与4a2bn+1是同类项，则m+n=（ ）．
6
— What's this _____ English?
— It's a book. [ ]
A. to
B. of
C. in
D. on
百部的主要功效是（）
A.化痰
B.止咳
C.平喘
D.清肺
E.泻肺
