AWS Organizations is a service that allows you to centrally manage and govern multiple AWS accounts. One of its key features is the ability to share resources across accounts within an organization. Specifically, AWS Organizations can be used to share pre-purchased Amazon EC2 resources, such as Reserved Instances and Savings Plans, across all accounts in the organization. This helps in cost optimization and resource management, as the payer account can purchase reserved capacity that is automatically shared with all linked accounts. The other options listed are not tasks that can be completed using AWS Organizations. Tracking application deployment statuses globally, removing unused and underutilized resources, and activating DDoS protection are not capabilities provided by AWS Organizations. Therefore, the correct answer is D: Share pre-purchased Amazon EC2 resources across accounts.