本课语言点
1. They are the hardest substance found in nature.
本句中found in nature是定语从句，修饰substance.定语从句中省略了that are.这种省略现象在定语从句中很常见，在前几个单元中，我们遇到过多次。请看下面的句子：
1） There are many books （that） I'd like to read. （有很多书我想看。）
2） He is a man （that） we all like and trust. （他是一个我们大家喜欢和信赖的人。）
3） This is the most interesting film （that） I have ever seen. （这是我看过的最有意思的电影）
先行词的前面有形容词最高级时，定语从句必须用that引导，而不用which.
本句中的hardest意思为“坚硬的”“坚固的”，而不是“困难的”。
mean是一个很常见的词，本句中的意思是“意味着”。mean还有“意欲，企图，打算”的意思。请看下面的句子，注意mean在各句中的意思和用法：
1） What do you mean by saying this to me？ （你对我说这个是什么意思？）
2） Friendship means everything to him. （友谊对他来说意味着一切。）
3） The teacher's praise meant so much to the children. （老师的表扬对孩子们来说很重要。）
4） I'm serious about this. I mean what I say. （我对此事是认真的，我说话算数。）
5） I'm sorry， I didn't mean to hurt you. （对不起，我无意伤害你。）
6） They meant to finish the work ahead of time. （他们的打算是提前完成这项工作。）
7） I meant to call you but I forgot. （我原打算给你打电话的，但我忘记了。）
cut在前一个句子中做动词用，意思是“切割”，在后一个句子中做名词用，意思是“切面”。
3. Diamonds are made from carbon.
由……制成，可以用be made from和be made of两个词组来表达。但是be made from通常指制成品已看不出原材料是什么，而be made of可以看出该物品由什么材料制成的。
4. Scientists know that the combination of extreme heat and pressure changes carbon into diamonds.
extreme在句中做形容词用，意思是“极度的”，如：
1） Extreme cold can wake a hibernating animal. （极度的寒冷能使正在冬眠的动物苏醒。）
2） They will have to endure extreme discomfort in winter. （冬天时，他们将不得不忍受极度的不适。）
change…into意思是“把…转变为…”，如：
1） Water changes into vapour when heated. （水加热后转变为蒸气。）
2） Go to the bank and you can easily change these dollars into RMB. （你去银行就能很容易地把这些美元换成人民币。）
5. Such heat and pressure exist only in the hot， liquid mass of molten rock deep inside the earth.
请注意such与so之间的不同用法。such后面接名词，而so后面接形容词或副词。如：
1） I don't believe he could make such a mistake. （我相信他不会犯这样的错误的。）
2） How can you go out on such a rainy day？ （在这样的雨天里，你怎么能出门？）
3） He spoke so fast that I couldn't follow. （他说话太快，我听不懂。）
4） I'm so glad you could come. （你能来我真高兴。）
mass在本句中的意思是“（聚成一体的）团、块”，比如：
1） a mass of hot air（一团热气）
2） a mass of sand（一堆沙）
3） Rain occurs when a mass of warm air is laden with water. （一团云聚集大量的水蒸气就形成了雨。）
Mass也可以做形容词用，意思是“群众的”、“大量的”，如：
1） a mass meeting （群众大会）
2） mass education （大众教育）
3） mass media （大众传媒）
4） Mass production could very well cut the cost. （大规模生产可以降低成本。）
6. It is thought that millions of years ago this liquid mass pushed upward through cracks in the earth's crust.
It is thought that…是一个很常用的句型，类似的句型在英语中很多，比如：
1） It is / was， has been…， reported that…
2） It is / was， has been…， stated that…
3） It is / was， has been…， pointed out that…
4） It is / was， has been…， mentioned that…
5） It is / was， has been…， believed that…
7. A. There are only four areas where very many diamonds have been formed.
B. The first known area was in India， where diamonds were found thousands of years ago.
定语从句可分为限定性定语从句和非限定性定语从句。A句是限定性定语从句，B句是非限定性定语从句。A、B两句中都是用关系副词where来引导定语从句，修饰表示地点的名词。请看下面的句子，注意限定性定语从句一般不用逗号隔开：
1） Is there a shop around where we can get some fruit？ （附近有什么商店可以买到水果吗？）
2） This is the place where we met yesterday. （这是我们昨天碰头的地方。）
3） The small town， where he once worked， has turned to be a modern city. （他曾经工作过的那座小城，已经变成现代化的城市了。）
8. In the 1600's…（十七世纪）
In the 1720's…（十八世纪二十年代）
In the 1800's…（十九世纪）
请注意年代的表达方法，以上的年代也可以表达为in the 1600s； in the 1720s； in the 1800s.如果我们要表达“在十七世纪初（中、末）期”，则可以说in the early（mid， late） 1600's/1600s.
9. Diamonds became very popular with the kings and queens of Europe.
become / be popular with / among是一个常用词组，意思是“受…欢迎”，
10. India's supply of diamonds was finally running out after 2，500 yeas of mining the stones.
Supply在句子中做名词用，意思是“供应”。Supply常常可以做动词用，意思是“供给，提供”。
run out是一个常用词组，意思是“用完，用尽”。请看例句：
1） Time is running out. We have to hurry. （时间快到了，我们得快点。）
2） My patience is running out. （我快要耐不住了。）
3） His luck seemed to have run out. （他的好运似乎结束了。）
我们也可以用run out来表达类似的意思，但run out of的主语应该是“某人”。如：
1） They have run out of money， so they have to find a job. （他们钱用完了，所以得找一份工作。）
2） I have run out of ink. （我的墨水用完了。）
11. People would pick up handfuls of gravel from the bottom of the streams and sort out the diamonds.
-ful通常加在名词后面，构成形容词，如care-careful，help-helpful.而本句中的handful是一个名词，意思是“一把”，在单词部分，我们已经提到过，英语中有不少这样的词，如：
1） He gave me a basketful of beaches. （他给了我满满一篮子桃子。）
2） She put a spoonful of salt in the soup. （她往汤里撒了满满一勺盐。）
3） Tom is carrying an armful of books. （汤姆抱着一捆书。）
sort out是一个常用词组，意思是“整理，分类”
bottom在句子中做名词用，意思是“底部”。bottom还有“尽头、末端”的意思
12. These diamonds were probably carried from where they were formed to India by great sheets of moving ice that covered parts of the earth 20，000 years ago.
where they were formed是where引出的名词性从句，作介词from的宾语。请看下面的句子：
He didn't say anything about where the accident took place. （他对事故在哪儿发生的只字未提。）
13. It flows over boards thickly coated with grease.
在本句中的定语从句thickly coated with greases前面省略了which/that are.coat一般做名词用，意思是“外套”或“（动物的）皮毛”。在本句中coat作动词用，意思是“在…上涂（包）着”，
14. Since diamonds stick to grease， they are left behind by the rocks and mud which flow down the tables.
Stick在本句中的意思是“粘住”。Stick to也可以表示“坚持，遵守”的意思。
leave behind在本句中的意思是“留下”，这个词组还可以表示“忘带；把…丢在后面”。例如：
1） Take care not to leave anything behind. （小心别丢下任何东西。）
2） Look forward to the bright future and leave all your worries and fears behind. （期盼光明的未来，把所有的担心和恐惧抛在身后。）
15. Experienced diamond miners can tell a diamond immediately.
句子中的tell意思为“判断；分辨；看出”。如：
I cannot tell her from her twin sister. （我无法分辨出她和她的孪生妹妹。）
短语表达
1. difference between…and
Will you please tell me the difference between a horse and a seahorse？
2.neither …nor
I have neither seen him nor heard from him since we last met.
3. look up
The little boy didn't dare to look up at his teacher.
4. a matter of
Don't panic. This is a matter of record and there is nothing to worry about.
5. throughout
He said that a person should be honest and upright throughout his life.
6. be satisfied with
The teacher was satisfied with the students' performance.
7. take place
The accident took place when people were all fast asleep.
8. lie in
The importance of this book lies in its later influence.
9. be classed as
He was classed as a genius.
10. hold good
This rule may hold good for you but not for me.
11. live on
Cows live on grass.
The old man lives on the government pension.
12. work wonders
I don't think this medicine will work wonders.
13. take in
Their club took in some new members last week.
14. suck up
The plants suck up a lot of water.
15. take up
He took up the newspaper and began to read.
She took up English when she was only five.
All the window seats had been taken up when I got on the bus.
责任编辑：小草
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