What bit should be set in the link state PDUs in an IS-IS level-1-2 router to indicate that they are a potential exit point out of the area ?

What bit should be set in the link state PDUs in an IS-IS level-1-2 router to indicate that they are a
potential exit point out of the area ?

A.
ATT (Attached )bit

B.
ABR (Area Border Rorter ) bit

C.
PN (Pseudonode )biy

D.
P(Partition) bit

E.
Down bit

F.
IS-Type bits