电力系统的电抗是因导线中通过()电流而使导线周围产生交变磁场所引起的。
A.直流
B.交流
C.雷击
D.内过电压
参考答案:B
The police __________the evidence by legal means that George murdered his wife. [ ]
A. achieved
B. gained
C. obtained
D. contained
在排水渠系规划设计中,确定各级排水沟道断面的主要依据是()
A.排水流量
B.设计水位
C.排水时间
D.渠道长度