This question belongs to the People domain because it focuses on enabling users, supporting adoption, and transferring operational knowledge to stakeholders. PMI guidance consistently treats communication, stakeholder engagement, and user readiness as key parts of successful delivery. When a new software solution is being introduced to a business team, the most effective way to promote knowledge transfer is end-user training. Training is interactive, allows users to ask questions, and helps ensure that the team understands how to use the solution correctly in real work scenarios.
Option A is too broad because project documents are generally not designed for user adoption. Option B can support training, but a handbook alone is passive and may not ensure understanding. Option D may help after go-live, but it is more of an ongoing support tool than the primary knowledge-transfer method. PMP-style thinking favors communication methods that promote real understanding, feedback, and readiness. Therefore, end-user training is the best answer because it directly supports practical adoption of the new solution and reduces the risk of misuse or low stakeholder acceptance.