---When did the film star arrive ________America, Jane?
--- Sorry, I don't know
A:at
B:in
C:on
D:of
如图,已知一动圆的圆心P在抛物线y= 12 x2﹣3x+3上运动.若⊙P半径为1,点P的坐标为(m,n),当⊙P与x轴相交时,点P的横坐标m的取值范围是____.
读图回答:
下列变化中,发生了化学变化的是( )