单相全波整流X线机,高压整流器的个数是()
A.6
B.4
C.2
D.8
E.12
参考答案:B
解析:单项全波桥式整流只能采用四管整流。
下列影响我国经济社会可持续发展的首要问题是[ ]
A.资源问题
B.人口问题
C.环境问题
D.社会问题
In history, many famous women _____ bravely_____ equal rights. [ ]
A. fought; for
B. had fought; for
C. fought; with
D. have fought; against