Which factor should be the reason for this situation?

Refer to the exhibit:

When implementing an LDP protocol, an engineer experienced an issue between two directly connected routers and noticed that no LDP neighbor exists for 1.1.1.1.

Which factor should be the reason for this situation?
A . LDP needs to be enabled on the R2 physical interface
B . R2 does not see any hellos from R1
C . LDP needs to be enabled on the R2 loopback interface
D . R2 sees the wrong type of hellos from R1

Answer: B