TOEFL Listening: ETS-TOEFL听力机经 - U44NR163ODPF315AP$

Why does the professor mention a fluctuation in the tilt of Earth's axis? A. To explain why ocean circulation patterns periodically change B. To suggest a possible contributing factor to the Arctic glaciation of three million years ago C. To suggest a reason that the ice age of three million years ago did not last long D. To explain why periods of cooling occur at regular intervals