ABC。 Since the coefficient of dynamic friction is 0.5 and the maximum acceleration provided by static friction is 5m/s2, when a constant force of 0.6N acts on the board, the system will move with the acceleration of a = FM+m = 0.60.2+0.1m/S2 = 2m/S2, and when the slider gets the speed of moving to the left, it will generate upward Lorentz force. When Lorentz force equals gravity, the elastic force between the slider and the plate is zero. At this time, Bqv=mg, and the solution is: v =10m/s. At this time, the friction disappears, the slider moves at a uniform speed, and the plate moves at a uniform speed under the constant force. A = FM = 0。 60.2m /S2 = 3m/S2. Therefore, A and B are wrong and C is correct.

D, if only the charge becomes negative, and other conditions remain unchanged, the system starts to move in a straight line with uniform acceleration, and the slider is subjected to Lorentz force vertically downward, so that there will be no relative sliding between the slider and the plate. Therefore, d is correct.

So choose CD.