When configuring a serial interface on a router, what is the default encapsulation?

A.
atm-dxi

B.
frame-relay

C.
hdlc

D.
lapb

E.
PPP

Explanation:
This question is to examine the data link layer protocols.
LAPB: Link Access Procedure Balanced for x.25 PPP: Point-to-Point Protocol HDLC: High-Level Data Link Control
Frame-relay and the three protocols above are data link layer protocols. HDLC is the default serial encapsulation protocol. The correct answer is C.