Final answer:
When a team chooses to focus on the highest priority Product Backlog items first, they are applying the principle of working software over comprehensive documentation.
Step-by-step explanation:
The principle from the Manifesto for Agile Software Development that is being applied when a team chooses to focus on the highest priority Product Backlog items first is Working software over comprehensive documentation. This principle emphasizes the importance of delivering working software that meets customer needs rather than spending excessive time on documentation.