A. Because they walk a lot and push a heavy can. Because they carry heavy water on their heads. C. Because it's difficult to walk on the bumpy road. D. Because it's difficult to pump water into a plastic can.
A. 各种水泥 B. 石膏 C. 沥青 D. 水玻璃
A. 熟料 B. 石灰 C. 石膏 D. 混合材料（或不掺）
A. 硅酸三钙 B. 硅酸二钙 C. 铝酸三钙 D. 铁铝酸四钙
A. 硅酸盐水泥生料的配制磨细 B. 硅酸盐水泥熟料的烧成 C. 通用硅酸盐水泥的粉磨 D. 通用硅酸盐水泥的水化
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