telecommunications providers responsibility begins?

What part of the network is the point where the responsibility of the administrator ends and the
telecommunications providers responsibility begins?

A.
last mile

B.
demarc

C.
router array

D.
PAD interface

Explanation:
Section Reference: Defining X.25
The demarc is the point where your responsibility as an administrator ends and the telecommunicationsor data
communications providers responsibility begins. The demarc can also be a network interface device or simple
networking jack.