Which TWO are core practices of Extreme Programming (XP)?
Test-driven development is a core XP practice: tests are written before code, then code is refactored until they pass. This satisfies XP's emphasis on continuous feedback and quality, distinguishing it from Scrum, which prescribes no engineering practices. TDD's red-green-refactor cycle directly supports XP's incremental design and collective ownership.
Why this answer
Test-driven development (TDD) is a core XP practice in which developers write an automated unit test before writing the code, then refactor once the test passes, giving rapid feedback and a safety net. Pair programming is also a core XP practice: two developers work together at one workstation, with one typing and the other reviewing, which improves design quality and knowledge sharing. By contrast, sprint review, product backlog grooming, and retrospectives are Scrum ceremonies/artifacts rather than XP's defining engineering practices, so they do not belong here.