A:①②③
B:仅有①②
C:仅有①③
D:仅有②③
有一簇电场线,电场方向如图所示.一带电粒子仅在电场力作用下,沿图中虚线从A运动到B,则( )
Mr. Brown is so strict ______ us that everyone in Grade 8 is scared _____ him.
如图,抛物线与x轴交于A(x1,0)、B(x2,0)两点,且x1<x2,与y轴交于点C(0,﹣4),其中x1,x2是方程x2﹣4x﹣12=0的两个根.