单项选择题

某石灰石试样含CaO约30％,用重量法测定其含量时，Fe3+将共沉淀。设Fe3+共沉淀的量为溶液中Fe3+含量的1％,则试样中Fe2O3的质量分数应不超过下列何数值时, 所产生的误差才能≤0.1％( )

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单项选择题

The Research and Development division of a company has recently designed a new coffee vending machine that is likely to sell very well in the market. It is compact, user-friendly, and provides unprecedented efficiency in terms of cost per cup. Consequently, the company fears that its competitors would soon mimic the design of their product and to protect its product, it is now seeking a （）. A. copyright B. patent C. trademark D. certification

多项选择题

锤式破碎机的锤子有（）

A.轻型锤子
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