电焊机倒换接头，转移作业地点或发生故障时，应（）电源。
A.切断
B.更换
C.远离
D.控制
参考答案：A
—Guess,how much does it cost?
—I think it costs_______15 and 20 dollars. [ ]
A. from
B. between
C. among
D. with
过冷度
