According to the meaning of the question, when the magnetic field as shown in the figure increases uniformly, a clockwise eddy electric field will be generated, so the positive charge will move clockwise under the action of electric field force.

According to the theorem of kinetic energy, in the process of one revolution, the increment of kinetic energy is equal to the work done by electric field force, that is, W=qU=q△B△tπr2=qkπr2, so C is correct and ABD is wrong.

So choose: C.