Unit 4 Astronomy the science of the stars课时作业

learning about language

一、 单词拼写

1． It cost him more than one________(十亿) dollars to complete the project.

2． "What happened？" John's mother asked him in a________(温和的) voice.

3． Before the Earth's protective________(大气层) was formed，there was no life except in the sea.

4． With the________(引力) of the moon and the sun each day，tides (潮汐) roll in and roll away.

5． Man-made________(卫星) are used for sending and receiving messages. 6．Smoking________(乘，增加) the risk of heart attacks and other health problems.

7．Eating too many desserts can be________(有害的) to one's teeth.

8．Global warming and________(气候) change problems are perhaps the greatest threats to our planet.

二、 原文填空

1． 随后它会变成什么没有人知道，直到38～45亿年前，这团尘埃才慢慢地形成一个固体的球状物。

________ ________ ________ ________ ________was uncertain until between 4.5 and 3.8 billion years ago when the dust settled into a solid globe.

2． 地球变得如此猛烈，以至于它的形状能否持久还不清楚。

The earth became________violent________it was not clear whether the shape would last or not.

3． 这就产生了一系列的反应，使得生命就有可能开始发展了。

This produced a chain reaction，which________ ________ ________ ________ ________ ________ ________.

4． 而当我试着向前迈步的时候，我发觉我被送出去很远，步子的跨度竟是在地球上的两倍，因而我摔倒了。

But when I tried to step forward，I found I was carried________ ________ ________ ________ on the earth and fell over.

5． "天哪，"我大声说。"引力改变了，走路也的确需要练一练了。" "Oh，dear，" I cried，"walking does need a bit of practice________ ________gravity has changed."

三、 单选

The top leaders of the two countries are holding talks in a friendly________.