Which two statements are true about IS-IS levels? (Choose two.)
A . Level 1 systems use a default route to reach AS external routes located in other areas.
B . Level 2 systems must use the loopback address as a part of the ISO network address.
C . Level 1 systems only from adjacencies with other systems that have different area IDs.
D . Level 2 systems do not advertise Level 2 routes into a Level 1 area by default.
Answer: AD