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Reasons for the British coal mining is called a “sick” industry today. 商品重要的化学性能有（） ["脆性","耐光性","硬度","弹性"] 铁碳合金相图对轧钢生产有什么意义？ 土壤物理机械性质不包括（）。 ["土壤粘结性","土壤粘着性","土壤耕性","土壤可塑性"] 燃料分哪几类？ 自然资源