The answer comes from Salesforce's separation of responsibilities. Use D. Partial Copy sandbox. Sandbox selection balances data copy, refresh cadence, isolation, testing depth, and cost. Smaller sandboxes fit independent build work; larger sandboxes fit integration and production-like testing.
The selected answer is stronger because it meets both the functional requirement and the maintainability requirement. In a Salesforce implementation, a solution that only works for one user, one page, or one data sample is not good enough. The correct feature has to behave consistently across the intended profiles, record types, apps, and devices that are part of the design.
The alternatives are plausible only if the requirement is read too narrowly. A (Full sandbox) should be rejected because Deployment tooling moves or validates metadata; it does not create the runtime business behavior itself. B (Developer File sandbox) would be fragile here because Deployment tooling moves or validates metadata; it does not create the runtime business behavior itself. C (Developer sandbox) does not fit cleanly; Deployment tooling moves or validates metadata; it does not create the runtime business behavior itself. A complete implementation should also check page assignment, field access, record ownership, and mobile behavior where those factors apply.
For sandboxes, the builder should match the environment to the work: isolated configuration, collaborative testing, data-dependent testing, or production rehearsal.
---