如图所示电路,在平行金属板M,N内部左侧中央P有一质量为m的带电粒子(重力不计)以水平速度v0射入电场并打在N板的O点.改变R1或R2的阻值,粒子仍以v0射入电场,则( )
—I often have hamburgers for lunch.
—You'd better not. It's bad for you _________ too much junk food.
下列关于电磁感应的论述中,正确的是( )