A:地域差异性
B:数量的有限性
C:整体性
D:分布的规律性
在真空中,电量为q1的点电荷产生的电场中有一个点P ,P点与q1的距离为r ,把一个电量为q2的试探电荷放在P点,它受的静电力为F ,则P点的场强大小为( )
The Greens ________live in the south of Asia . They don't want to move to the north because they ________ the cold weather.
They should do exercises as ________ as possible to keep _________.