焊接工作电压指()。
A、更换电焊条的电压;
B、电弧燃烧的电压;
C、引弧时的电压;
D、短路电压。
参考答案:B
Why not describe what you saw that day___? It will surely help the police to find out who were to blame for the terrible accident.
A.in order
B.in return
C.in detail
D.in charge
种子学创始人是()。
A.Nobbe
B.Cieslar
C.Wiesner
D.Sachs