—Did Jack come back early last night?

—Yes.It was not yet eight o'clock ______ he arrived home.[ ]

A. before  

B. when  

C. that  

D. until

在微机中，微处理器的主要功能是进行_______。

A．算术运算

B．逻辑运算

C．算术及逻辑运算

D．运算及控制