A Network Has Several Routers Running IS-IS Layer 1/Layer 2

Multiple Choice

A network has several routers running IS-IS Layer 1/Layer 2 mode on the same Ethernet segment. Which action reduces the number of the IS-IS adjacencies to a minimum in this segment?

A) Make sure that the interface priority on the backup DIS is lower than the primary DIS
B) Change all routers connected to this segment to a single-level area
C) Define only one router on the segment to be DIS
D) Change half the routers to be Layer 1-only and the other half to be Layer 2-only on this segment