EJA型智能变送器在使用终端BT200进行调零后，在（）秒内不能断电，否则零点将恢复到原始值。
A.10
B.15
C.30
D.45
参考答案：C
按要求完成句子，每空一词。
1. They went to the mountains last Monday. (就画线部分提问)
________ ________ they ________ last Monday?
2. The people there were unfriendly. (就画线部分提问)
________ ________ the people there?
3. We visited some museums in Beijing. (就画线部分提问)
________ ________ you ________ in Beijing?
4. Lucy is a thirteen-year-old girl. (改为同义句)
Lucy is ________ ________ ________.
5. You can't give him the watch. (改为肯定祈使句)
________ ________ ________ to him.
如图所示的电路，伏安法测定自感系数较大的线圈的直流电阻，线圈两端并联一个电压表，用来测量自感线圈两端的直流电压，在实验完毕后，将电路拆去时应（ ）
A．先断开开关S1
B．先断开开关S2
C．先拆去电流表
D．先拆去电阻R
