【单选题】互感器检定中使用的电源及调节设备,应保证具有足够的容量及调节细度,并应保证电源的频率为(),波形畸变系数不得超过5%。
【单选题】—I saw you come to school by bus this morning. —Oh, I _______ come to school by bus, but it is raining today.
【单选题】How did it that the child dropped out of school?
【单选题】I ______ an old school friend in Oxford Street this morning.
【单选题】— I saw you come to school by bus this morning. — Oh, I come to school by bus, but it is raining today. [ ]