【单选题】Perhaps you ______ leave now. Your friend may be waiting for you outside.
【单选题】零件在切削加工过程中使用的基准叫作( )。
【判断题】如果没有稀缺性,就不会出现国际贸易摩擦。
【判断题】霍乱弧菌可以引起人类疾病,其中霍乱毒素是最主要的毒力因子
【单选题】— Could I watch TV for another while, mum? — Oh, dear, if you ______. [ ]
【单选题】You _____ such a serious mistake if you had followed his advice.