熔化焊过程中出现有害因素的强烈程度受（）影响。
A、焊接规范
B、焊接设备
C、焊接材料
参考答案：A
—Hello! Could I speak to the headmaster?
—______, Please call back later. [ ]
A. Wait a minute
B. Hold on for a moment
C. Speaking
D. Sorry, he isn't here at the moment
