TOEFL Listening: ETS-TOEFL听力机经 - 0E54T91B48999KW1P$

Why does the man talk about birds that migrate at night? A. To demonstrate that he understands the professor's recommendation B. To give examples of what he wants the professor to explain C. To give an alternative explanation of the hibernation of the Common Poorwill D. To ask whether he should change his topic to the sleeping behavior of birds