The most valid generalization about the team-building activity preferences of the employees would come from 400 randomly chosen employees from the list of all employees.
This sample is likely to provide a more representative cross-section of the entire employee population, thereby minimizing bias and ensuring that a variety of perspectives and preferences from different departments, levels of experience, and demographics are included in the results. In contrast, the other options may introduce bias, as they focus on specific subsets of employees rather than the overall employee base.