To which IS-IS area does this router belong?

Refer to the Exhibit.

Refer to the router configuration shown in the exhibit.
To which IS-IS area does this router belong?

A.
Area 49

B.
Area 0100

C.
Area 49.2020

D.
Area 49.2020.0100.1001.0001

Explanation:
IS-IS Areas

An IS-IS network is a single autonomous system (AS), also called a routing domain, that consists of end systems and intermediate systems. End systems are network entities that send and receive packets. Intermediate systems (routers) send, receive, and relay (forward) packets.
IS-IS does not force the network to use a hierarchical physical topology. Instead, a single AS can be divided into two types of areas: Level 1 areas and Level2 areas. A Level1 area is similar to an OSPF stub area, and a Level2 area interconnects all Level1 areas. The router and its interfaces reside within one area, and Level2 routers share link-state information. No IS-IS area functions strictly as a backbone.

Level 1 routers share intra-area routing information, and Level2 routers share interarea information about IP addresses available within each area. Uniquely, IS-IS routers can act as both Level1 and Level2 routers, sharing intra-area routes with other Level1 routers and interarea routes with other Level2 routers.

The propagation of link-state updates is determined by the level boundaries. All routers within a level maintain a complete link-state database of all other routers in the same level. Each router then uses the Dijkstra algorithm to determine the shortest path from the local router to other routers in the link-state database.

Network Entity Titles and System Identifiers

In IS-IS, special network addresses are called network entity titles (NETs) and take several forms, depending on your network requirements. NET addresses are hexadecimal and range from 8octets to 20octets in length. Generally, the format consists of an authority and format Identifier (AFI), a domain ID, an area ID, a system identifier, and a selector. The simplest format omits the domain ID and is 10octets long. For example, the NET address 49.0001.1921.6800.1001.00 consists of the following parts:

* 49AFI
* 0001Area ID
* 1921.6800.1001System identifier
* 00Selector

The system identifier must be unique within the network. For an IP-only network, we recommend using the IP address of an interface on the router. Configuring a loopback NET address with the IP address is helpful when troubleshooting is required on the network.

IS-IS Overview
http://www.juniper.net/techpubs/software/junos-security/junos-security10.0/junos-security-swconfig-interfaces-and-routing/protocols-is-is-overview-section.html