Two sliders A and B with mass M1 and M2 are horizontally connected by a light spring and placed on the horizontal table top My answer is C. I think there is a problem My problem stem is the problem in the screenshot, I just don't want to type it out again

This question examines Newton's second law, Newton's third law and stress analysis
When the two sliders move at a constant speed, the analysis of the overall force, the force F and the total friction, are reversed. Then, for a, three forces, tension F, friction f a, elastic f n, there is f-fa-f n = 0; similarly, for B, two forces, elastic f n and friction F B, there is f n-f B = 0. It is concluded that f n = F B; F = FA + F n
When the pulling force is removed, for a, FA + FN = m1aa; for B, FN FB = m2ab
So, ab = 0; the direction of AA is opposite to the velocity of a, so, AA

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