[单项选择]Light travels very fast. It moves at a speed of 300,000 kilometers a second. Light reaches us from the moon in less than a second and a half. The moon is about 382,000 kilometers away.
Light from the sun reaches us in 8.5 minutes. The sun is about 149,840,000 kilometers from the earth.
The other stars are farther away than the sun. Light from the nearest star reaches us in about four years. When you look at a star, you do not see its present condition. You see it as it used to be. Light from some stars takes hundreds of years to reach us. We never see a star as it is now. We see it as it was long ago; perhaps hundreds of thousands of years ago.
Astronomers (天文学家) watch the stars through big telescopes. The world’s biggest telescope is in Russia. The next biggest is in-the United States. With these great telescopes astronomers can see stars and other things very far away. Some of these things are not only stars. They are great groups of stars.
The light of the sun reac
A. more time than
B. less time than
C. as much time as
D. less years than

[单项选择]Light travels very fast. It moves at a speed of 300,000 kilometers a second. Light reaches us from the moon in less than a second and a half. The moon is about 382,000 kilometers away.
Light from the sun reaches us in 8.5 minutes. The sun is about 149,840,000 kilometers from the earth.
The other stars are farther away than the sun. Light from the nearest star reaches us in about four years. When you look at a star, you do not see its present condition. You see it as it used to be. Light from some stars takes hundreds of years to reach us. We never see a star as it is now. We see it as it was long ago; perhaps hundreds of thousands of years ago.
Astronomers (天文学家) watch the stars through big telescopes. The world’s biggest telescope is in Russia. The next biggest is in-the United States. With these great telescopes astronomers can see stars and other things very far away. Some of these things are not only stars. They are great groups of stars.
The earth is nearer to __
A. the stars... the sun
B. the moon... the sun
C. the stars... the moon
D. the sun... the moon

[单项选择]It’s known to all that light travels much more quickly than sound does. A. 所有知道的全部内容就是光跑的速度要比声音快得多。 B．所有的人都知道光跑的速度要远远快过声音跑的速度。 C．众所周知，光传播的速度比声音传播的速度快得多。 D．关于那种光所得知的内容就是比声音传播得要快。

[单项选择]

If you see someone drowning, speed is very important. Once you get him out of the water, if he isn’t breathing, you have four minutes before his brain is completely damaged. Support his neck, tilt his chin upwards. This stops the tongue blocking the air way in the throat and is sometimes enough to get him breathing again. If that doesn’t work, start mouth-to-mouth breathing. Press his nostrils (鼻孔) together with your fingers. Open your mouth wide and take a deep breath. Blow into his lungs until his chest rises, and then remove your mouth and watch his chest fall. Repeat twelve times a minute, keep going until professional help arrives.
To bring a child back to life, keep your lips around its mouth and nose and gently blow into its mouth. Give the first four breaths as quickly as possible to fill the blood with oxygen. If, in spite of your efforts, it starts turning blue grey colour, and you can feel no pulse, then pressing its chest is the last chance of savi
A. have to pull of your clothes first
B. should hurry to get him out of water as soon as possible
C. should first make out who he is
D. ought to throw a lifeboat to the person first

[填空题]Because light travels (fast) ______ than sound, lightning is seen before thunder(雷) is heard.

[填空题]Due to the fact that light travels ______ (fast) than sound, lightning is seen before thunder is heard.

[填空题]Due to the fact that light travels______(fast)than sound,lightning is seen beforethunder is heard．

[填空题]Due to the fact that light travels______(fast) than sound, lightning is seen before thunder is heard.

[填空题]In police work speed is often very vital, so computers are ______.