完全垄断企业的需求曲线（）。
A.向右上方倾斜，斜率为负
B.向右上方倾斜，斜率为正
C.向右下方倾斜，斜率为正
D.向右下方倾斜，斜率为负
参考答案：D
We used to _____every day when we were children.
A．swim
B．swimming
C．be swimming
D．going swimming
总集
