The sportsman ________ save a drowning boy that afternoon;  the boy's parents appreciated him very

much.[      ]

A. might  

B. could

C. was able to  

D. must

项目可行性研究是在( )之后所做的进一步的调查和研究。

A．投资机会研究

B．项目建议书

C．项目评估

D．专题规划研究