单轨吊承载部分共有()种起吊梁。
A、1
B、3
C、2
D、4
参考答案:B
— David, why are you so excited?
— My father has made a that he will take me to Tibet next month.
A. face B. promise C. mistake
对地电压在250v以上的电气设备为高压设备。