Explanation

For high availability requirements, deploying an application across multiple Availability Zones (AZs) is the correct approach because:

• Availability Zones are physically separate data centers within an AWS Region
• Each AZ has independent power, cooling, and networking
• Deploying across multiple AZs provides fault tolerance - if one AZ fails, the application can continue running in other AZs
• This architecture ensures high availability and resilience

Why other options are incorrect:

• Single Availability Zone: Provides no redundancy - if that AZ fails, the entire application goes down
• AWS Direct Connect: This is for dedicated network connectivity, not for high availability deployment
• Reserved Instances: This is a billing/pricing model for cost savings, not a deployment strategy for high availability

High availability in AWS is achieved through multi-AZ deployments, which is a fundamental cloud architecture principle.