ISUP消息的路由标记由（）组成。
A.OPC
B.DPC
C.SLS
D.CIC
参考答案：A, B, C
船体结构所能承载的吃水称（）。
I have been teaching for over twenty years, but never _____ a girl as bright as Lily.
A．I have met
B．I had met
C．have I met
D．had I met
