To make our city more beautiful, rubbish ________ into the river.           [ ]

A. needn't be thrown      

B. mustn't be thrown          

C.can't throw              

D. may not throw

人才开发工作的（）指人才开发的运作是否合乎逻辑和规律，是否经得起理论推敲和实践的检验。

A.理性

B.有效性

C.经济性

D.时效性