Most of her spare time ______ , she still kept on her research in the library.

A．occupied

B．had been occupied

C．to be occupied

D．was occupied

8051单片机的定时器T1用作计数方式时计数脉冲是（）。

A.由T1（P3.5）输入

B.由内部时钟频率提供

C.由T0（P3.4）输入

D.由外部计数脉冲计数