【单选题】The happiest people are not those ________ have the best of everything, but ________ make the best out of everything.
【单选题】发电机星型联接时,三相绕组的三个始端U1、V1、W1引出的三根线称为
【单选题】You will easily know ________ video recorders are the same.
【多选题】发电机三相绕组的三个始端U1、V1、W1引出的三根线称为
【单选题】Those of us who work in chemical laboratories,should have their lungs checked quite regularly.