【单选题】She said her brother () in Beijing. He () to Japan on business last week.
【单选题】She said her brother ____ in Beijing. He ______ to Japan on business last week.
【单选题】PN 结具有单向导电性,是因为正偏时 ,反偏时 。
【判断题】数据库营销起源于20世纪80年代中期美国的直接信函及广告协会
【单选题】数据库营销起源于20世纪()年代中期美国的直接信函及广告协会。
【单选题】老式澡堂中水池的水,是将水蒸汽直接通人冷水中,使冷水加热。这种换热方式属于
【单选题】She said her brother ____ in Beijing. He ______ to Japan on business last week.