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
