1. [单选题]清空某台Cisco路由器NVRAM中的全部配置信息，正确的配置操作是______。
A. Router(config)clear running-config
B. Routerwirte erase
C. Router(config)erase running-config
D. Routererase running-config
2. [单选题]RIPv2路由信息协议是一种基于哪一协议的应用层协议( )
A. IP
B. TCP
C. UDP
D. ICMP
3. [单选题]The most commonly used locking level in implementing concurrency control is at which of the following levels?
A. database
B. table
C. record
D. field
