Option (C) is the correct answer. The provided text explicitly states under the section 'Force for Drifting' that 'The polar-fleeing force relates to the rotation of the earth.' It further explains that the earth has a bulge at the equator, which is caused by this rotation. Options (A), (B), and (D) are incorrect based on the context; the text clarifies that tidal force is related to the attraction of the moon and the sun, while polar-fleeing force is specifically linked to rotation.