What is the purpose of a chassis cluster?

A.
Chassis clusters are used to aggregate routes.

B.
Chassis clusters are used to create aggregate interfaces.

C.
Chassis clusters are used to group two chassis into one logical chassis.

D.
Chassis clusters are used to group all interfaces into one cluster interface.

Explanation:
The Junos OS achieves high availability on Junos security platforms using chassis
clustering. Chassis clustering provides network node redundancy by grouping two like
devices into a cluster. The two nodes back each other up with one node acting as the
primary and the other as the secondary node, ensuring the stateful failover of processes and
services in the event of system or hardware failure. A control link between services
processing cards (SPCs) or revenue ports and an Ethernet data link between revenue ports
connect two like devices. Junos security platforms must be the same model, and all SPCs,
network processing cards (NPCs), and input/output cards (IOCs) on high-end platforms must
have the same slot placement and hardware revision.
The chassis clustering feature in the Junos OS is built on the high availability methodology of
Juniper Networks M Series and T Series platforms and the TX Matrix platform, including
multichassis clustering, active-passive Routing Engines (REs) , active-active Packet
Forwarding Engines (PFEs), and graceful RE switchover capability.