根据三极管内PN结的单向导电性,如果正反向电阻(),说明其基本是好的。
A、零
B、无限大
C、相差较小
D、相差较大
参考答案:D
_____ Joseph off at the airport, Sally finished her work earlier.[ ]
A. Having seen
B. Seen
C. To see
D. To be seen
列车空调采用的是车顶集中式空调单元。