经鼻比经口气管插管深（）
A.1cm
B.2～3cm
C.4cm
D.5cm
E.6cm
参考答案：B
--Do you know what caused the accident? --- No, not yet. The matter _____.
A．is being looked into
B．was being looked into
C．looked into
D．is looked into
MS_SQL SERVER是()。
A．数据库
B．数据库系统
C．数据处理系统
D．数据库管理系统
