TOEFL Listening: ETS-TOEFL听力机经 - 44W141L9G5C3WML0P$

According to the professor, what were the accomplishments of the International Astronomical Union in the 1920s? A. Assigning scientific names to the traditional constellations B. Determining the approximate number of stars in each constellation C. Deciding which star configurations should be considered constellations D. Dividing the night sky into well-defined regions