2.loudly(loud) with fire and rock.They were in time to produce many things，which were 3.to make(make) the earth's atmosphere.As the earth cooled down，water began to appear on its surface.It allowed the earth to dissolve 4.harmful(harm) gases.Then life began to develop.

Small plants multiplied and filled the oceans and seas with oxygen.This encouraged the 5.development(develop) of early shellfish and fish.Land animals such as insects，reptiles and dinosaurs 6.appeared(appear) after green plants began to grow.Small clever animals spread all 7.over the earth.They are putting too much carbon dioxide into the atmosphere,8.which prevents heat from escaping from the earth into space.9.Whether life will continue on the earth for millions of years to come will depend on whether this problem can 10.be solved(solve)．

1．No one knows exactly how the earth began，as it happened so long ago.

[句式分析]　本句为复合句，how引导的是宾语从句；as引导的是原因状语从句。

[自主翻译]　没有人确切地知道地球是怎样形成的，因为在很早以前它就形成了。

2．What is even more important is that as the earth cooled down，water began to appear on its surface.

[句式分析]　本句为复合句，what引导的是主语从句；that引导的是表语从句，在表语从句中又含有一个as引导的伴随状语从句。

[自主翻译]　更为重要的是，随着地球的冷却，地球的表面开始出现了水。

3．So whether life will continue on the earth for millions of years to come will depend on whether this problem can be solved.

[句式分析]　本句为复合句。So whether life will continue on the earth for millions of years to come是主语从句；whether this problem can be solved是宾语从句，作介词on的宾语。

[自主翻译]　所以，在未来的数百万年中，生命能否在地球上延续取决于这个问题能否得到解决。

Ⅰ.阅读理解

　　The earth is the only planet that scientists think has life.Why does the earth have life while the other planets(行星) don't？For one thing，the earth has just the right temperature.As the third planet from the sun，the earth seems to be just the right distance away.The planets which are closer to the sun are so hot because their surfaces are baked(烘烤) in the sun.The farthest planets are cold balls.

When the earth developed-which scientists believe may have happened about 4 billion