—Susan, why are you still here? They are all ready to start.        

—I'm sorry, but I ________when to start.          [ ]

A. was told    

B. told            

C. tell              

D. wasn't told

下列描述中，错误的是( )。

A．Java要求编程者管理内存

B．Java的安全性体现在多个层次上

C．Applet要求在支持Java的浏览器上运行

D．Java有多线程机制