Question

        Why does the sky change colors?

   What is the sky? How high is it? What color is it? What birds can live above it? These questions are difficult to answer,aren’t they?

    In fact,the sky has no color. Then why does the sky look blue?

    We know that there is air around the world. When planes fly,they need air to lift their wings. Planes can9t fly very high. That is because the air gets thinner when they go higher. The same will happen to us if we go high enough. If we go up about 1,200 kilometers from the earth,we’ll find no air there. Some birds can fly into the sky as high as a plane,but they cannot fly or live without air.

    Looking up above us,you will see the blue sky with white clouds. It is usually light blue. The color will be bluer when you see on the top of a high mountain. And you will see fewer clouds in the sky between you and the sun.

   Sometimes the sky doesnH look blue. When the sun rises or falls,you will see red,orange,and other colors in the sky. Such are the most beautiful moments of the day.

    Who can see the colors of the sky high above the earth? The astronauts!They can see those beautiful colors of the sky from the outer space. However,before flying into the outer space,they sit in a spaceship high above the earth,and there is no air at all. The sky will be that dark and its color will be black.

   Now you may understand that we see colors because the air scatters (使散射) the sunlight. Light travels through the air. Without air,there would be no light or colors.

52. Planes can't fly as high as possible because .

   A. the sky is blue

   B. the wings are heavier

   C. the sky has no color

   D. the air becomes thinner

53. When you stand on the top of a high mountain,you will see

   A. more air       B. bluer skies

   C. more colors   D. more clouds

54. In Huzhou,we might see many colors in the sky at during the day.

   A. 6:00 a. m.      B. 9:00 a.m.

   C. 1 ：00 p. m.     D. 3：00 p. m.

55. The sky changes colors because.

   A. it's colorful itself

   B. the world is colorful

   C. the sunlight has colors

   D. the air scatters the sunlight

Answer 1

52. D 53. B 54. A 55. D

[阅读D篇短文大意]文章主要介绍了天空为什么有变化

多端的颜色。

52. D 由第二段中的"Planes can't fly very high. That is because the

air gets thinner when they go higher” 可知，飞机不能尽可能 高地飞行是因为随着高度增加空气会变得越来越稀薄。

53. B 由第四段中的” The color will be bluer when you see on the

top of a high mountain"可知，当你站在高山顶上，你会看到 更蓝的天空。

54. A由第五段中的"When the sun rises or falls,you will see red ,

orange,and other colors in the sky” 可知答案为 A.

55. D由最后一段中的we see colors because the air scatters (使散射) the sunlight”可知D项符合题意。