A network engineer is using IS-IS IGP protocol to design a network.
Which three design elements should be used to divide the network into a hierarchy of areas?
(Choose three.)

A.
Core routers will be only level-2.

B.
Routers on the edge of the network will be only level-1.

C.
Router between core and edge routers will be level-1-2.

D.
Core routers will be only level-1.

E.
Routers on the edge of the network will be only level-2.

F.
Router between core and edge routers will be only level-2.

G.
Router between core and edge routers will be only level-1.