To obtain the most valid generalization about the preferred team-building activity among all employees, the best option from the provided choices is:
C) 400 randomly chosen employees from the list of all employees.
This sample is random and includes a larger number of employees, which helps reduce bias and gives a more accurate representation of the entire workforce's preferences. The other options have limitations, such as focusing on specific groups (like only female employees or long-term employees) which may not reflect the preferences of the entire employee population. Option D is too small to adequately represent the diverse opinions of the entire company.