【简答题】Have you not heard the President over and over again address some of the major ch______ that exist in the present era?
【简答题】下列卤化硼分子中,大 π 键最弱的是(
) (8.0分)A. BF 3 B. BCl 3 C. BBr 3 D. BI 3
【简答题】The government couldn't rest on its present conditions and must press ahead with major policy ch______.
【单选题】若属性 X 函数依赖于属性 Y 时,则属性 X 与属性 Y 之间具有 __________ 的联系。