A complete and realistic backlog must include not onlyfunctional storiesbut alsonon-functional and support taskssuch as infrastructure setup, analysis, and design. ThePMI Agile Practice Guide (Section 5.2: Backlog Composition)andMike Griffiths' PMI-ACP Exam Prep Book (Chapter 6: Adaptive Planning) emphasize including all types of work in the backlog to ensureaccurate effort planning. * Option Dis correct: effort must includetechnical tasks, not just feature delivery. * Option Asuggests speculation on velocity and cost increases, which is unreliable. * Option BandC(adding buffers or padding estimates) violate agile's principle of transparency and simplicity.