| 21. | The law of conservation and transformation of energy is the chief basis of physical, astronomical and chemical reasoning as well as of engineering practice. |
| 能量守恒和能量转换的定律，不仅是工程实践的主要根据，而且也是物理、天文以及化学等方面推理的主要根据。
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| 22. | A lot of poisonous waste comes from that chemical factory. |
| 那家化工厂放出许多有毒废物。
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| 23. | More than 100 chemical elements are know to man, of which, about 80 are metals. |
| 已知有100多种元素，其中大约80种是金属。
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| 24. | The use of chemical fertilizer is bringing the crops on nicely. |
| 使用化肥使庄稼长势良好。
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| 25. | Chemical analysis of water yields hydrogen and oxygen. |
| 水经过化学分解会产生氢和氧。
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| 26. | It is a frequent phenomenon in chemical analysis. |
| 这是化学分析中的常见现象。
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| 27. | They've just built a new chemical plant. |
| 他们刚建成了一个新化工厂。
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| 28. | chemical additives in food |
| 食品中的化学添加剂
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| 29. | white chemical compound that is added to foods, usu meat, to make their flavour stronger |
| 谷胺酸钠; 味精
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| 30. | rivers polluted with chemical waste from factories |
| 受到工厂排放的化学废料污染的河流
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