I arrived at the airport _ _ the plane had taken off. [ ]
A. while
B. before
C. after
答案:C
民兵应急分队紧急出动演练轻武器完好率应达到()以上。
A.80%
B.85%
C.90%
D.95%
屋面结构层板缝中浇灌的细石混凝土上应填放背衬材料,上部嵌填密封材料,并应设置保护层。( )