舌杆应至少离开下颌前牙舌侧龈缘（）
A.9～10mm
B.7～8mm
C.5～6mm
D.3～4mm
E.1～2mm
参考答案：D
Mary had to go to a meeting,so she left her children________at home.[ ]
A．playing
B．played
C．to play
D．having played
对于50层的建筑，沉降观测应从（）施工时开始。
A.基础
B.架空层
C.一层
D.二层
