Though he tried many ways to solve the problem, ______ worked; he decided to turn to his tutor for

help.    [ ]

A. none of which      

B. all of them    

C. none of them      

D. all of which

健康教育的基本理论中没有（）。

A.选择理论

B.知信行理论

C.因果理论

D."力扬"理论

E.行为干预理论