As shown in the following figure, what are the reasons why the two routers cannot establish an IS-IS neighbor relationship? (Multiple Choice)
A . The IS-IS process IDs of the two routers are different from each other.
B . The system IDs of the two routers conflict with each other.
C . The IS-IS cost types of the two routers are different to each other.
D . The IS-IS preference values of the two routers are different to each other.
E . The interfaces of the two routers are on different network segments.
Answer: BC