下列材料中可用作承重结构的为（）

重写句子：At the international museum, you can find ancient Egyptian art. You can explore African artifacts there. You can discover beautiful textiles from around the world there.(parallel structure)

炎热夏季大体积混凝土施工时,必须加入的外加剂是（）

重写句子：We slipped on the road when we could see no lights in the heavy rain that night.(periodic sentence)

重写句子：Fossil fuels are non-renewable. We need to find alternative energy sources. (compound sentence)

评价材料抵抗水的破坏能力的指标是（）

重写句子：Alan passed the test. Alan had studied hard. Alan had understood the material.(complex sentence)

某一材料的下列指标中为常数的是（）

重写句子：When we are relieved of working pressures of the office, we can enjoy happiness and relaxation at home.(modifying phrase)

重写句子：The teacher returned the homework. The teacher noticed the error.(complex sentence)