Which bit should be set in the link-state PDU of an IS-IS L1/L2 router to indicate that it is a pote

Which bit should be set in the link-state PDU of an IS-IS L1/L2 router to indicate that it is a potential
exit point of the area?

A.
the ABR bit

B.
the ATT bit

C.
the down bit

D.
the P bit