问题：

[单选]

Nexus# conf t 
Enter configuration commands， one per line. End with CNTL/Z. 
Nexus（config）# interface Loopback10 
% Permission denied  Nexus（config）# ？ 
no Negate a command or set its defaults 
username Configure user information. 
end Go to exec mode 
exit Exit from command interpreter 
What is the reason why this user is not able to enter configuration commands？（）

A .  The user did not enter enable prior to going into configuration mode.
B .  The software license installed on Nexus is Layer 2 only， which does not allow the creation of Layer 3 interfaces.
C .  The user RBAC role is set to network-operator.
D .  The user failed authentication and user access defaulted to read-only mode.
E .  The AAA server is currently not responding.