D
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 clouds. 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 (气象学家).
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 have your brains. 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 local forecast.
What are you seeing when you look at a cloud? “A picture of what moisture (水气) 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 clouds over a day or two tells you a lot more than a single 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.
53. According to the passage, ordinary people can tell the weather because __________.

A. they can look up at the sky	B. they can read weather writings
C. information is stored in computers	D. clouds signal the weather to come

54. Your advantage in weather forecast is that __________.

A. you can keep weather patterns in mind.

B. you have more powerful computers at home

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

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

55. A cloud is formed when __________.

A. there are droplets in the air	B. light is scattered
C. moisture exists in the form of invisible gas	D. water vapor changes to liquid water

56. This passage mainly tells us about how__________.

A. to become a weather forecaster	B. to collect data directly
C. to be an assistant to a meteorologist	D. to keep an eye on the weather