防错设计可以分为：预防错误的发生，错误发生后及时可以发现，（）。
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You need to configure fine-grained access control to external network resources from within your database. You create an access control list (ACL) using the DBMS_NETWORK_ACL_ADMIN package. Which statement is true regarding the ACL created?（）
A. It is a list of remote database links stored in the XML file that are available to the users of the database.
B. It is a list of users and network privileges stored in the XML file according to which a group of users can connect to one or more hosts.
C. It is a list of users and network privileges stored in the data dictionary according to which a group of users can connect to one or more hosts.
D. It is the list of the host names or the IP addresses stored in the data dictionary that can connect to your database through PL/SQL network utility packages such as UTL_TC
典型的局域网可以看成由以下三部分组成：网络服务器、工作站、（）。
A. IP地址；
B. 通信设备；
C. TCP/IP协议；
D. 网卡。
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