---Where ________ you last night? I called you, but got no answer.

---Sorry. I ________ out with my brother.

A．was; were

B．were; was

C．did; were

D．did; was

CPU输出数据的速度远远高于打印机的打印速度，为解决这一矛盾，可采用 ______。

A．并行技术

B．通道技术

C．缓冲技术

D．虚存技术