A:A=2,φ= π4
B:A=2,φ= π6
C:A=2 2 ,φ= π3
D:A=2 2 ,φ= π6
“(王景)迁庐江(位于安徽)太守。先是,百姓不知牛耕,致地力有余而食常不足。……景乃驱率吏民,修起芜废,教用犁耕,由是垦辟倍多,境内丰给。”《后汉书》的这段记载反映当地( )
— Let's go dancing tonight!
— Sorry, I ______.I have to go to a meeting.