States had at least three social levels, usually, an upper class of rulers, a middleclass comprised of managers and merchants, and a lower class of crop producers and agricultural laborers.

国家中至少有三种社会阶层，上层阶级（执政），中产阶级（商人，管理者）和下层阶级（农民，工人）。

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Because of the erratic rainfall patterns in Australia, it is often considered that soil moisture sets the upper limit on crop yield potential.

由于澳大利亚降雨类型多变，人们常认为土壤水分给作物产量定了上限。

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Practising intensive farming and loosening upper soil layer could hold rainfall water and make it penetrate into soil effectively, which could improve soil quality and crop moisture condition.

精耕细作、疏松表层、保持水土、充分接纳雨水就地入渗增大土壤水库贮水，可有效地改善农田土壤和作物水分条件。

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For investors who can afford to employ the cream of the crop, the upper echelon of investment advisors can beat the indexes on a regular basis.

FORBES: Money Managers Only Make Sense For The Rich