Questions 33 to 36 are based on the following passage：

　　Wouldn't it be great if you could just look up at the sky and read the weather forecast right away?

　　Well, you Can. The forecast is written in c1ouds. If you can read that writing，you can tell something about the atmosphere. With some practice， you can become a pretty good weather forecaster.Who knows，you might even do as well as meteorologists.

　　Meteorologists use much more information than just the appearance of the clouds to make their forecast.They collect data from all over the world. Then they put it into powerful，high-speed computers.

　　This does give meteorologists an advantage，because they can track weather patterns as they move from west to east across the country.

　　But you have an advantage，too.You can look at the sky and get your data directly.A meteorologist uses a computer forecast that’s several hours old to make a 1ocal forecast.

　　What are you seeing when you look at a cloud?”A picture of what moisture is doing in the atmosphere,” says meteorologist Peter Leavit . There’s moisture throughout the atmosphere. Most of the time you don't see it，because it's in the form of an invisible gas called water vapor.

　　Sometimes，the temperature of the air gets cold enough to cause the water vapor to change to liquid water.That’s called condensation， and we see it happen all the time (for example，when humid air from the shower hits the cold glass of a mirror). When enough water vapor condenses，droplets form in the air.These droplets scatter light.A cloud is seen.

　　Watching c1ouds over a day or two tells you a lot more than a sing1e cloud about the weather to come， Changes in clouds show changes in the atmosphere.

　　You should begin to notice patterns. Certain clouds， fol1owing each other in order， can signal an approaching storm. But don’t take our word for it; see for yourself.

　　33.This passage main1y tells us about how__________.

　　A. to become a meteorologist

　　B. to keep an eye on the weather

　　C. to be an assistant to a meteorologist

　　D. to change water vapor to liquid water

　　34.According to the passage，an ordinary person might do as well as a meteorologist in weather forecast_____________.

　　A. with the help of the high-speed computers

　　B. through a complex process of calculation

　　C. with some simple practice looking up at the sky

　　D. consulting a weather station

　　35.Meteorologists make their weather forecast__________.

　　A. by collecting data from all over the world

　　B. by putting this date into powerfu1， high?speed computers

　　C. by ca1culating and ana1yzirig this data

　　D. all above

　　36.Your advantage in weather forecasts is that____________.

　　A. you have more powerful computers at home

　　B. your brain works as well as a high-speed computer

　　C. you observe the sky and obtain your data directly

　　D. meteorologists give their data to you as soon as they get them