开关柜出厂试验,合闸装置在额定电源电压的()范围内,应可靠动作。
A.80%~110%
B.80%~120%
C.85%~110%
D.85%~120%
参考答案:C
用介词at / in / on填空。
1. We have history _____ the afternoon.
2. I go to school _____ half past seven.
3. Do you have a piano lesson _____ Saturday?
4. They do their homework _____ ten o'clock.
5. What time do you go to school _____ the morning?
某人要到一座高层楼的第8层办事,不巧停电,电梯停开,如从1层走到4层需要48秒,请问以同样的速度走到八层,还需要多少秒( )
A.48
B.50
C.64
D.20