用浮筒液位计测量液位，如果与浮筒底部相联的管道被堵住，则液位显示（）。
A.保持某值不变
B.跑到零
C.跑最大
参考答案：A
Someone is knocking at the door. It ____ my mother. It's time for her to be back. [ ]
A. can be
B. may not be
C. must be
D. mustn't be
多层砖房构造柱应伸入室外地面标高以下()。
A.250mm
B.500mm
C.1000mm
D.1500mm
