character: Emma
topic: 土壤保护的重要性
grade: 6
subject: Foreign Language
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character: Emma
topic: 如何保护土壤
grade: 6
subject: Foreign Language
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character: Emma
topic: 土壤的生态作用
grade: 6
subject: Foreign Language
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character: Emma
topic: 可持续农业与土壤保护
grade: 6
subject: Foreign Language
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