We see the hello interval on R1 is not the same as R2 (and you can verify with the “show ip ospf interface command”) -> There is a hello and dead interval mismatch problem. We should configure “no ip ospf hello-interval 25″ on R1.
Note: Maybe there are some versions of this question in the exam. For example there are some reports saying that Ethernet0/1 on R1 is shutdown (and this is the correct choice in the exam). So please be careful checking the config on the routers before choosing the correct answers.