Explanation:

Scalability is the correct answer because it refers to the ability of a system to handle increased workload by adding resources. In this scenario:

1. Scalability allows the EC2 fleet to automatically scale up or down based on traffic demands
2. AWS provides Auto Scaling groups that can automatically add or remove EC2 instances based on metrics like CPU utilization or network traffic
3. This enables the system to accommodate unpredictable traffic increases without manual intervention

Why other options are incorrect:

• Resilience: Refers to the ability to recover from failures and continue operating, not specifically about handling traffic increases
• Security: Relates to protecting data and resources from unauthorized access, not traffic management
• Agility: Refers to the speed of provisioning resources and responding to changes, but doesn't specifically address handling unpredictable traffic increases

Key AWS Services:

• Amazon EC2 Auto Scaling: Automatically adjusts the number of EC2 instances
• Elastic Load Balancing: Distributes traffic evenly across instances
• CloudWatch: Monitors metrics to trigger scaling events