如图所示,abcd是一矩形的四个顶点,且ab=cd=20cm,ad=bc=40cm,电场线与矩形所在平面平行,已知a点电势为7V,b点电势为13V,则( )
A:场强大小一定为E=30V/m
B:cd间电势差一定为6V
C:场强方向一定由b指向a
D:c点电势可能比d点低
如图,DE与△ABC的边AB,AC分别相交于D,E两点,且DE//BC.若AD:BD=3:1, DE=6,则BC等于( ).
⑴Bob is a good football player. ____
⑵Last Saturday, my father and I watched a basketball game.____
⑶This is our team.____
⑷—Who won? ____
—Tom's team won.
⑸My brother is a policeman.____
A. B. C.
D. E.
下图为“某地区1月平均气温分布图”(阴影部分为陆地),N地的气候类型是( )
如图,∠ACB=9O°,D为AB中点,连接DC并延长到点E,使CE=14CD,过点B作BF∥DE交AE的延长线于点F.若BF=10,则AB的长为 ____