Which reason for the problem is the most likely?

Refer to the exhibit.

After you applied these configurations to routers R1 and R2, the two devices could not form a neighbor relationship .

Which reason for the problem is the most likely?
A . The two routers cannot authenticate with one another.
B . The two routers have the same area I
D . The two routers have the same network I
F . The two routers have different IS-types.

Answer: C

Explanation:

For those asking about the password, area authentication doesn’t prevent neighboring to come up because it is carried only in LSP, CSNP and PSNP messages and not in IIH messages. https://www.cisco.com/c/en/us/support/docs/ip/integrated-intermediate-system-to-intermediate-system-is-is/13792-isis-authent.html