很久以前，人们对宝石的化学成分没有研究。
Long ago, people did not investigate the chemical composition of stones.
植物和动物体对环境化学成分的变化非常敏感。
Plant and animal life is sensitive to changes in the chemistry of the environment.
本文对奶及乳制品中的化学成分进行了研究。
Chemical compound of milk and dairy products have been studied.
本文对奶及乳制品中的化学成分进行了研究。
Chemical compound of milk and dairy products have been studied.
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