Because the wooden block moves in a straight line at a uniform speed twice, the pulling force is equal to the sliding friction, that is, the pulling force and the sliding friction are equal, so B is incorrect and C is correct.
(2) As can be seen from the figure, under the same tensile force, the distance and speed of the two movements of the wood block are different.
According to W=Fs, the work done on the wood block twice is different, so A is incorrect;
According to the relationship between kinetic energy and the mass and velocity of the object, it can be known that the kinetic energy obtained by the wood block twice is different, so D is incorrect.
So choose C.