My mother is ______________ English teacher.[ ]
A. a
B. the
C. an
答案:C
To our great________, Geoffrey's illness proved not to be as serious as we had feared. [ ]
A. anxiety
B. relief
C. view
D. judgment
谐波源是指向()注入谐波电流或在()中产生谐波电压的电气设备。
A.动力电网,供配电网
B.公用电网,照明电网
C.公用电网,动力电网
D.公用电网,公用电网