Please study the exhibit shown above carefully, and answer the following question.
Which connection user the default encapsulation for serial interfaces on Cisco routers?

A.
The serial connection to the MidEast branch office.

B.
The serial connection to the DeepSouth branch office.

C.
The serial connection to the NorthCentral branch office.

D.
The serial connection to the Multinational Core.

Explanation:
On the basis of the configuration on Dubai provided in the exhibit, we know that the encapsulation
types of different interfaces are as follows:
Serial 1/0 : encapsulation frame-relay
Serial 1/2 and Serial 1/3 : both interfaces are encapsulated PPP
Serial 1/1: There is no related encapsulation information displayed, so its default encapsulation
type is HDLC .
Based on the network topology provided in the exhibit, the interface Serial 1/1 is connected to the
router Mideast of the branch office, so the encapsulation type of the router Mideast is by default.
The default encapsulation on a serial interface is HDLC. The original HDLC encapsulation was
defined by the International Organization for Standards (ISO), those same folks who developed
the OSI model. The ISO version of HDLC had one shortcoming, however; it had no options to
support multiple Layer 3 routed protocols. As a result, most vendors have created their own form
of HDLC. Cisco is no exception because it has its own proprietary form of HDLC to support
various Layer 3 protocols such as IPX, IP, and AppleTalk.
The Serial connection to the Dub<i branch office using the default encapsulation type. You can
change using:
* encapsulation <type> command on interface