Final answer:
Supplementing a primary firewall with a standby one for backups in case of failure is known as High Availability. It ensures operational continuity and reduces system downtime to maintain business operations.
Step-by-step explanation:
When a single firewall is supplemented with a second standby firewall that is ready to assume responsibility in the event of the primary firewall's failure, we are using what is known as High Availability (B). High availability is a design approach in computer systems and networks that ensures a certain degree of operational continuity during a given measurement period. The goal of high availability systems is to minimize downtime and ensure business continuity. In contrast, Clustering (A) involves connecting multiple computers to work together, Component Redundancy (C) refers broadly to the duplication of critical components or functions of a system with the intention of increasing reliability of the system, and Load Balancing (D) is the process of distributing network or application traffic across several servers to ensure no single server becomes overwhelmed. Supplementing with a standby firewall is specifically an example of component redundancy aimed at achieving high availability.