通电螺线管附近小磁针静止时,N极指向如图所示,则螺线管的a端是 ____ 极,电源的 ____ 端是正极,增大电源电压小磁针的指向 ____(选填“改变”或“不改变”).
Don't open the door. It's cold. Please ____ the door.
如图,在多面体ABCDEF中,底面ABCD是以AD,BC为腰的等腰梯形,且DC=12AB,∠DAB=60°,EF∥AC,EF=12AC,M为AB的中点.
(I)求证:FM∥平面BCE;
(Ⅱ)若EC⊥平面ABCD,求证:BC⊥AF.
Mr. Smith didn't go to the movie. He went swimming, ________.
19世纪60年代,在世界近代浪潮的冲击下,东西方掀起了国家体制改革。
请结合图片,回答问题: