During the development phase, which typically consists of a series of sprints, the primary focus is on building and verifying the product increment. Developers take user stories from the sprint backlog and implement the required functionality by configuring the Guidewire platform (C). Concurrently, Quality Analysts (QAs) test the completed user stories to ensure they meet the predefined acceptance criteria and function as expected (B). These two activities form the core loop of building and validating the software within each sprint of the development phase.

A. User stories are checked into the production code branch by developers: Code is checked into feature or development branches; merging to a production branch happens after extensive testing and approvals, typically during a release phase.

D. User stories are all evaluated for inclusion in project scope: This activity occurs during the Inception or Discovery phase, before the development phase begins.

E. User stories are initially prioritized for scheduling in sprints: High-level prioritization occurs in Inception, and detailed sprint-level prioritization happens during sprint planning, just before development on that sprint starts.

Guidewire SurePath Agile Methodology Guide, Section: "Project Phases - Development". This section details the activities within the development phase, emphasizing the cycle of configuration by developers and testing by QAs for each user story within a sprint.

Guidewire Business Analyst Fundamentals Courseware, Module: "The Guidewire Project Lifecycle". The course materials describe the development phase as the period where user stories are built (configured) and tested against their acceptance criteria.