原始社会部落联盟首领产生的方法是[ ]
A.通过比武
B.父传子
C.民主推举
D.年长者为首领
答案:C
Don't forget ___________ an umbrella ___________ you. It's going to rain. [ ]
A. to take;to
B. taking;to
C. to take;with
D. taking;with
交流电动机定子绕组做交接时交流耐压标准为()。
A、0.5(2Un+1000)V
B、0.75(2Un+1000)V
C、(2Un+1000)V
D、1.5(2Un+1000)V