Refer to the exhibit. Hosts on the 192.168.1.0 network cannot communicate with hosts on the 172.16.1.1 network. The network administrator has run the show ip route command on R1.

Refer to the exhibit. Hosts on the 192.168.1.0 network cannot communicate with hosts on the 172.16.1.1 network. The network administrator has run the show ip route command on R1. 

What could be the cause of this problem?

The FastEthernet interface on R1 is disabled.

Autosummarization is enabled on R1.
The serial interface S0/0/0 of R1 is administratively down.
No static route or routing protocol is configured.