A:x|x≤2
B:x|0≤x≤2
C:{x|x≥2或x≤0}
D:x|x≥0
如图所示,a,b,c为电场中同一条电场线(直线)上的三点,c为ab中点。a、b电势分别为Ua=5V,Ub=3V;下列叙述正确的是 ( )
⑴Open the door, please. ____ A.
⑵Close the window, please. ____ B.
⑶Open the window, please. ____ C.
⑷Close the door, please. ____ D.