When you look up into the sky at night, have you ever felt that your eyes are playing tricks on (捉弄) you? It seems that the stars are moving all the time.
Actually, there is nothing wrong with your eyes. This twinkling effect is called scintillation (交光). Scintillation happens because of air movements in the earth’s atmosphere (大气). Light is “bent (弯曲的)” when it travels through different parts of the earth’s atmosphere. As the air in the earth’s atmosphere is moving all the time, the light from the stars looks as if it is moving too.
The same thing also happens to things on the ground. On a very hot and shiny day, if you look at the road, the image in the distance is not clear and things move slightly. You can also see the same effect if you drop a rock into water. The rock appears a little unclear under the moving water.
This twinkling effect causes a lot of problems for astronomers (天文学家) since they cannot observe the stars clearly. A telescope (望远镜) was sent into space so that the air movements in the atmosphere could be avoided (避免). It took a long time to build the space telescope but finally in 1990, a huge space telescope called the Hubble Space Telescope was successfully sent into space. Since then, astronomers have many important observations that have helped people understand space better.
根据短文内容，选择最佳选项。
What happens to the light from the stars we see when the air in the earth’s atmosphere is moving?

A．It looks even brighter.

B．It looks as if it is bent.

C．It looks as if it is moving.

D．It looks like drops of rain.

Scintillation also happens on 　　　　 according to the passage.

A．rainy days	B．shiny days
C．cloudy days	D．windy days

What can you see when you drop a rock into the water?

A．The rock gets broken.

B．The rock becomes unclear.

C．The water becomes much polluted.

D．The water does not move anymore.

The underlined word “observe” means “　　　　”.

A．watch

B．listen

C．draw

D．explain

Why is scintillation a problem for astronomers?

A．The stars never stay still.

B．It makes the stars too dark to see.

C．It makes astronomers feel too hot to work.

D．Astronomers cannot observe the stars clearly.