—Where is kate? —She ______ in her room. [ ]
A. read
B. reads
C. is read
D. is reading
答案:D
在一棵二叉树上第5层的结点数最多是( )。
A.8
B.16
C.32
D.15
对于新材料、新工艺、新结构形式的结构构件和跨度较大的屋架、桁架等结构构件,在使用状态短期试验荷载作用下的持续时间不宜少于()
A.24h
B.18h
C.12h
D.30min