火灾自动报警中，当客房设置专用扬声器时，其功率不宜小于（      ），一般取一瓦。
A、1.0W
B、1.5W
C、3W
D、5W

(多选题)Which of the following are true according to the l...

多项选择题(多选题)Which of the following are true according to the lecture? A.
Zhang Qian had been sent twice to the west. B.
Roman royal families were very much attracted by clothes made of the silk. C.
Xuan Zang wrote Journey to the West to record his experience in India. D.
Marco Polo arrived China at Yuan Dynasty.

A． B． C． D．

单项选择题

A．
B．
C．
D．

我国直流传动机车绝大多数都是采用(  )的励磁方式。A．他励 B．串励 C．复励 D．并励

单项选择题我国直流传动机车绝大多数都是采用(  )的励磁方式。