Which of the following answers can be verified as true based on the following command output from Router R1?（） R1#show ip ospf virtual - links Virtual Link OSPF_VL0 to router 4.4.4.4 is up Run as demand circuit DoNotAge LSA alloweD. Transit area 1, via interface FastEthernet0/1, Cost of using 3

• A、R1 is configured with  an area 0 virtual - link 4.4.4.4 cost 3 command.
• B、The ping 4.4.4.4 command on R1 must currently be successful.
• C、R1's Fa0/0 OSPF cost is 3.
• D、4.4.4.4 is known to R1 based on a Type 1 LSA in area 1.