A:液泡由小变大,紫色变浅
B:液泡由大变小,紫色变深
C:液泡由大变小,紫色变浅
D:液泡由小变大,紫色变深
________ Tom ________ Mary speaks good Chinese, so they can communicate with these Chinese students very well.
平行板电容器的两板A、B接于电池两极,一带正电小球用绝缘细线悬挂在电容器两板之间,细线与竖直方向夹角为θ,如图,那么( )