Which parts of the Scrum framework most directly support validating product assumptions?

• AA usable Increment that people can react to, a Sprint of a month or less that caps how far an unchecked assumption can be built on, and a Sprint Review where the Increment is inspected with stakeholders and the Product Backlog is adapted
• BThe Daily Scrum and the Sprint Retrospective, because they surface impediments
• CThe Definition of Done alone, since quality is what makes evidence reliable
• DThe Sprint Backlog, because it holds the plan for the Sprint