Routers R1 and R2, currently EIGRP neighbors over their Fa0/0 interfaces (respectively),both use EIGRP authentication. Tuesday at 8 p.m. the neighborship fails. Which of the following wo uld not be useful when investigating whether authenticationhad anything to do with the failure？（）
- A debug eigrp packet
- B show key chain
- C show ip eigrp neighbor failure
- D show clock