正解:B
To complete the NAT configuration on R1, the commands should specify which interfaces are inside and outside relative to NAT. The correct set of commands would be:
R1(config)# interface GigabitEthernet 0/0
R1(config-if)# ip nat inside
R1(config)# interface GigabitEthernet 0/1
R1(config-if)# ip nat outside
This configuration designates the interfaces on R1 that will participate in NAT: GigabitEthernet 0/0 as the inside interface where the local network resides, and GigabitEthernet 0/1 as the outside interface facing the external network.