Which command prevents R1 from sending OSPF hello packets on interface GigabitEthernet0/0?

The passive-interface command, configured under the OSPF routing process (config-router), prevents OSPF hello packets from being sent out of the specified interface. This effectively stops OSPF from forming adjacencies on that interface. It's commonly used on interfaces connected to end-user segments where OSPF neighbors are not expected or desired, saving resources and increasing security. ip ospf hello disable is not a valid OSPF command. ip ospf hello-interval 0 would set the hello interval to 0 seconds, which is an invalid and non-functional configuration for OSPF. passive-interface Gig 0/0 configured in global configuration mode (config) is incorrect because passive-interface is an OSPF-specific command and must be configured within the OSPF routing process.