听力原文：W: This is Lian, and, like many of our listeners out there, I'm tired. I'm tired in the morning, I'm tired in the afternoon, and I'm really tired at night. And frankly, I'm tired of being tired. My excuse is that I have two small children who sleep a little, and wake up a lot. Dr. Walsleben, why are we all so tired? M: We're probably tired because we don't make sleep a priority. And I think as a young mother and a career woman, your days are pretty well filled, and I would suspect that you probably think you can do without sleep or at least cut your sleep short, and one of the things that happens is that we forget that sleep loss accumulates, so even one bad night, teamed with another will make an effect on our performance the following day. The other aspect, which you did touch on, is that even though we may sleep long periods of time, the sleep may not be really of good quality. W: How serious of a problem is sleep deprivation? M: Well, it can be very serious, because lack of sleep can affect our performance. It's not… we can get cranky and all that, but if our performance is poor, and we are in a very critical job, we can have a major incident. And there have been many across society in which sleep and fatigue were issues. The Exxon Valdez was one in which the captain got a lot of attention, but the mate who was driving the ship had been on duty for 36 hours… But you can read your local papers every weekend, you'll see a car crash with probably a single driver at around 2 or 3 am, no reason who they would happen to drive off the road, and we all believe that that's probably a short sleep event that occurred when they weren't looking for it. W: Dr. Walsleben, I know how this sleep deprivation affects me. By the end of the day, with my children, I'm tired and cranky, I'm not making good parenting decisions, I don't have a lot to give my husband when he comes home, and then I just feel too tired to exercise. So I think, 'Oh, I'll eat or I'll have a big cup of coffee, and that will give me the energy that I don't have naturally.' Are these pretty common effects of sleep deprivation amongst your patients? M: They're very common, and so many people accept them. W: I would even say that by Friday afternoon, I'm afraid to get behind the wheel of a car, because I just feel like I am not a safe driver on the road. That's how tired I am by Fridays. M: I think it's great of you to have recognized that… and that's a real, major concern for most of America's workers. By Friday, everyone seems to be missing, probably, 5 hours of sleep. This huge deficit can be very serious, if not fatal, to people, and of course people who drive cars for long periods of time are at greater risks. W: Thanks Dr. Walsleben, at least I don't feel very tired after talking with you. M: Thank you. Questions: 11.What is the interview mainly about? 12.Why does Lian mention her experience as a parent? 13.Which of the following effects of sleep deprivation is NOT mentioned in the interview? 14.What does Dr. Walsleben mean when he says 'I think it's great of you to have recognized that'? 15.What does Dr. Walsleben imply about tired drivers? (31)