Choice C is the best answer. In (lines 1-3"Lady ...the"), the narrator states that Lady Carlotta "stepped out on to the platform of the small wayside station and took a turn or two up and down its uninteresting length" in order to "kill time." In this context, Lady Carlotta was taking a "turn," or a short walk, along the platform while waiting for the train to leave the station.
Choices A, B, and D are incorrect because in this context "turn" does not mean slight movement, change in rotation, or course correction. While Lady Carlotta may have had to rotate her body while moving across the station, "took a turn" implies that Lady Carlotta took a short walk along the plat-form’s length.