Refer to the exhibit.
Router>enable Router#configure terminal Router(config)#hostname R1 R1(config)#username R2 password cisco R1(config)#interface serial 0/0/0 R1(config-if)#encapsulation ppp R1(config-if)#ppp authentication chap R1(config-if)#exit
Router>enable Router#configure terminal Router(config)#hostname R2 R2(config)#username R1 password cisco R2(config)#interface serial 0/0/0 R2(config-if)#encapsulation ppp R2(config-if)#ppp authentication pap R2(config-if)#exit
Based on the configurations shown, why is the serial link in up/down status?

A.	Mismatch hostnames
B.	Passwords are in plain text
C.	Mismatch of authentication type
D.	Wrong configuration mode for command input