Formation of Soil 12/4/15

0 5 词汇卡 morelandj

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问题		答案
a mixture of sand, silt, soil, clay, rock and humus (plant and animal remains) 开始学习		soil
when forces on Earth breaks rocks apart or wear rock away 开始学习		weathering
the uppermost 5 to 20 cm of soil with a high concentration of organic matter and microorganisms where almost all of the biological activity in soil takes place 开始学习		topsoil
easily broken down by biological activity, especially bacteria in the soil 开始学习		biodegradable
to break down into smaller, more basic parts 开始学习		decompose

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