iMC UBA的作用是（）。
A.给用户下发访问权限
B.掌握用户上网行为
C.管理网络设备
D.AAA认证，授权，计费
参考答案：B
The headmaster often comes to teachers’ office to __________some difficulties. [ ]
A. look into
B. look after
C. look for
D. look up.
主动脉瓣关闭不全可出现
A．交替脉B．水冲脉C．不整脉D．间歇脉E．奇脉
