Router R2 is having adjacency problems with Router R1. Router R2 is stuck in ExStart state.

What is causing the problem?

A.
There is a physical and data link layer problem between R1 and R2.

B.
There is a misconfigured IP address on the R2 interface.

C.
The hello and dead intervals on R2 do not match R1.

D.
The interface MTU setting on R2 does not match R1.