In Brazil, it is considered normal to show up for a social event ________.
A. Ten to fifteen minutes early
B. Ten to fifteen minutes late
C. Fifteen minutes to an hour late
D. One to two hours late.
查看答案
( )必须选用水硬性胶凝材料。
A. 干燥环境下
B. 潮湿环境中
C. 寒冷环境下
D. 高温环境下
胶凝材料按成分可分为____胶凝材料、____胶凝材料。
气硬性胶凝材料只能在____凝结硬化,也只能在____保持和发展其强度。