TOEFL Listening: ETS-TOEFL听力机经 - 934VRRSUZ31NL7W5P$

Why does the professor mention the position of Polaris, the North Star? A. To help explain how astronomers measure the relative positions of stars B. To help explain how star catalogs have evolved over time C. To help explain why different stars are seen from different locations on Earth D. To help explain why the sky looks different at different times in history