混凝土细集料的粗细程度,通常有粗砂、中砂、细砂和特细砂之分。
参考答案:对
The smile on my father’s face showed that he was ______ with me. [ ]
A. sad
B. pleased
C. angry
D. sorry
高层建筑应设立防火警示标志。楼层内不得堆放易燃可燃物品。在易燃处施工的人员不得吸烟和随便焚烧废弃物。