题干
31．----- Oh, my goodness! My laptop must have got stolen．
----- But where _____ a thief have entered the house with all the doors and windows still locked?
A：should
B：could
C：dare
D：did
答案(点此获取答案解析）
B
表示的平面区域为面积为16，那么z＝2x－y的最大值与最小值的差为（ ）
