Ⅱ 重点句子讲解：
1.They hope to develop an early warning system that can be used to forecast earthquakes so that lives
can be saved . 他们希望研究出一种能够用来预报地震的早期预警系统，以拯救生命。
该句中that引导的定语从句修饰an early warning system .
so that 引导目的状语从句说明前边的复合句。
2.The nations that are actively involved in earthquake prediction programs include Japan， China， Russia， and the United States.
定语从句中短语 be involved in … “参加，参与”
Eg ：All the children were involved in the school play. 所有的孩子都参加了学校排练的剧。
The four men were all involved in organizing and carrying out the murders. 这四个人都参与组织和实施了这些谋杀案。
3.These networks are on the alert for warning signs that show the weakening of rock layers that can precede an earthquake.
这些网络始终处于戒备状态，搜索地震前岩石可能松动的警告迹象。
第一个定语从句修饰warning signs
第二个定语从句修饰the weakening of rock layers
4.Scientists speculate that the amount of radon increases in the ground when rocks layers shift， exposing new rocks ， and thus more radon.
科学家推测，当岩层位移时，露出新岩石，地下氡的含量会增加，因此就产生更多的氡。
exposing new rocks ， and thus more radon.分词短语作动词shift的结果状语
5.However， all the scientists agree that more data is necessary to prove that radon levels in water are
associated with the possible birth of an earthquake.
be associated with ： 与…。有关
但是，所有科学家都同意还需要有更多的数据才能证明水中氡含量与可能发生地震之间有着联系。
在宾语从句中又有一个that 引导的宾语从句
6.While this is a small start， it is still a beginning.
尽管这是一个小的开端，但毕竟还只是处于初始阶段。
While 在本句中引导让步状语从句，意为“尽管，虽然”
conj.
（1）引导让步状语从句
（2）引导时间状语从句时表示“在…之间”
（3）表示两个并列关系的转折，“而，然而”
n.一回儿
eg. Wait a while 等一会儿
still conj. 毕竟，尽管如此
ad.还，仍然，仍旧
n.静物
a.静止的，不动的
stand still 站着不动
Ⅲ 补充语法：
不定式在句中的作用
不定式除了不可以作谓语之外，它可以担任句子的成分有：主语、表语、宾语、
定语、状语和补语。 常用来表示未来要做的事，以及愿望、打算、决心等
1.主语
To sum up experience is important.
It is important to sum up experience.（ it 为形式主语）
2.表语
Our aim （goal） is to pass the exam. Our objective is to master English.
master v. 掌握
n.主人