The poor student, all________books and living expenses are paid for by the Hope Project, has

been admitted to Peking University. [ ]

A. of whom  

B. whom  

C. of whose  

D. of his

一辆汽车从A地到B地的速度为每小时30千米，返回时速度为每小时20千米，则它的平均速度为（）。

A．24千米/小时

B．24.5千米/小时

C．25千米/小时

D．25.5千米/时