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A．Stay at home.B．Visit the exhibition later.C．He will go there individually.D．Go to vi
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A．It is well known all over the world.B．It has become the topic of an article.C．It has
听力原文： The idea of fighting a noise by making more noise sounds strange, but that's exactly what motor engineers are doing in Germany and some other countries.
Carmaker's research and development laboratories have already proved that mixing in more noise with the help of loudspeakers can reduce the unwanted noise.
Physicists have known about the technique for a long time. Sound is made up of pressure waves in the air. If two sound waves of the same frequency mix so that the highest point of one wave happens at the same time with the lowest point of the other wave, the result is no sound. Therefore, by producing a perfect copy of the noise and delaying it by half a wave cycle, we can kill the unwanted noise. Using this technique many carmakers are racing to develop noise-killing systems both inside and outside the cars.
Another good thing about the use of noise-killing systems is that it saves the need for a silencer, which not only reduces the weight of a car, but also makes the motor burn less oil and work better.
Some engineers believe that the noise-killing system will be used in most cars in 1996. But the carmakers haven't decided if they will put it into production because it would add several hundred dollars to the cost of their cars.
(30)
听力原文：M: How was your weekend？
W: It was awful.
M: Awful？ Really？ But I thought you were supposed to be going on a trip. Did it get cancelled？
W: No, unfortunately, it wouldn't been better if it had.
M: What do you mean？
W: Well, five of us were supposed to go to Chicago in Lisa's car.
M: Yeah？
W: And we were going to stay at Sue's parents' house, which is in Chicago.
M: Right？
W: So it's about a four-hour trip, and we were going to get there on Friday evening, spend Saturday sightseeing, and come back last night so we could go to classes this morning.
M: OK. That sounds like a good plan. So what went wrong？
W: What didn't go wrong？ First of all, we were all crammed into Lisa's tiny car with all four bags.
M: Sounds pretty uncomfortable.
W: Hold on. I'm just getting started. Remember how hot it was this weekend？
M: Yeah, It was so bad I had to get out of the library. I ended up going to the beach both days.
W: Well, we were stuck in Lisa's car Friday afternoon and the air conditioner wasn't working.
M: Why didn't you open the windows？
W: We did, but the breezes blowing in weren't exactly cool.
M: I'll bet you were glad to get to Chicago.
W: That's the worst part. We never made it. Mary started feeling sick from all the heat, so Lisa tried driving faster to find Mary something to drink. To make a 10ng story short, the car broke down and we were stranded till this morning in some small town near the Indiana border.
M: Couldn't Sue's parents come pick you up？
W: They were out of town.
(20)
A．They think it useful.B．They think it valueless.C．They think it a waste of time.D．The
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