电机运转时轴承温度过高，主要原因是（)
A. 润滑脂牌号不合适
B. 润滑酯质量不好或变质
C. 轴承室中润滑脂过多或过少
D. 润滑脂中夹有杂质
依据环境要素的不同，我们可以将环境分为（)。
A. 大气环境
B. 水环境(湖泊环境和河流环境)
C. 海洋环境
D. 土壤环境
E. 生物环境(森林环境、草原环境)
Ben Franklin was versatile in every possible field and he was chiefly noted as a man of civic mind. （)
The Last of The Mohicans were the best work by Edgar Allan Poe. （)
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