Which statement is true regarding the IS-IS designated intermediate system (DIS)?

Which statement is true regarding the IS-IS designated intermediate system (DIS)?

A.
The DIS function is used only on broadcast or multi-access networks.

B.
The DIS function is used on both broadcast and point-to-point link types.

C.
On a broadcast network, adjacencies are formed only between the non-DIS nodes and the DIS
to help reduce adjacency overhead.

D.
IS-IS supports a backup DIS mechanism to provide rapid failover in the event of a DIS failure.

Explanation: