The use of multiple Availability Zones involves distributing AWS resources such as EC2 instances across separate, isolated locations within a region. This practice is vital for high availability because it protects applications from failing due to an outage in a single location. Each Availability Zone is a separate data center with redundant power, networking, and connectivity to provide fault tolerance. Other answers involve redundancy but do not specifically refer to the geographic distribution of data centers that ensure high availability. For example, auto-scaling helps meet demand but doesn't protect against data center outages, and the use of an AWS Region doesn't inherently provide high availability unless resources are distributed across its Availability Zones.