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Therefore, in these two processes, the work done by overcoming the electric field force is equal, indicating that the potential of ab is equal, and the potential of ab is higher than that of point C. 。

A. If the electric field is uniform along the positive direction of the Y-axis, the potentials of two points ab are not equal, which does not meet the question. So, A is wrong.

B. If the electric field is uniform and strong in the negative direction along the X axis, and the potentials at two points ab are equal, then moving the positive charge to two points A and B to do negative work is in line with the meaning of the question, so B is correct.

C. If the electric field is formed by a negative point charge at a certain position in quadrant IV, then the electric field force at points A and B will move the positive charge to do positive work, and the electric potential energy will be reduced, which does not conform to the meaning of the question. So, C is wrong.

D. If the electric field formed by the positive point charge at a certain position in quadrant IV is located on the perpendicular line of the connecting line A and B, and the potentials at two points ab are equal, it is in line with the meaning of the question to move the positive charge to the electric field force at two points A and B to do negative work. Therefore, d is correct.

So choose BD.