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。)
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