[听力原文]M: How far do you live from Beijing University, Professor LiW: It takes about 20 minutes to drive from my home to the university. But during the rush hour it takes 10 minutes longer. How much time does it take if Professor Li drives from the university to his home during the rush hour（） A: About 20 minutes. B: About 30 minutes. C: Less than 20 minutes. D: At least more than 30 minutes.