Mr Smith________his living by teaching ten years ago and he________greatly from his work. [ ]

A. earned; earned  

B. earned; gained

C. gained; gained  

D. gained; earned

CPU通过接口输出控制一组发光二极管的亮/灭，应采用的传送方式是( )

A．无条件传送
B．查询传送
C．中断传送
D．DMA