矿用隔爆磁力起动器的隔爆换向开关与前门之间有可靠的（）闭锁装置。
A、电气
B、机械
参考答案：B
—Please tell Nana she has won the first prize in the teaching skill contest in April.
—_________! She never did so well before.
A．Congratulations
B．Good luck
C．That’s right
D．What a good surprise
为什么焊前焊条要严格烘干？
