若方程x2+y2﹣x+y+m=0表示圆,则实数m的取值范围是( )
A:m<12
B:m>12
C:m<0
D:m≤12
小明同学从家乘公交车上学,车以54km/h合____ m/s匀速行驶,小明看到窗外路边的树木快速后退,他是以____ 做为参照物,经过了10分钟,到达了目的地,汽车行驶了____ km.
We have to our sports meeting till next week because of the bad weather.