Choice "D" is correct. The statement of functional expenses is required for voluntary health and welfare organizations but is optional for all others. The best example of a voluntary health and welfare organization of the three choices given is a shelter for the homeless, the organization that likely receives most of its operating income from general donations and is organized to improve the overall health and welfare of a specific segment of society.
Choice "a" is incorrect. The statement of functional expenses is required for voluntary health and welfare organizations but is optional for all others. An art museum is not a voluntary health and welfare organization.
Choice "b" is incorrect. The statement of functional expenses is required for voluntary health and welfare organizations but is optional for all others. A private foundation is generally not a voluntary health and welfare organization (at least not as clearly a voluntary health and welfare organization as a homeless shelter).
Choice "c" is incorrect. The statement of functional expenses is required for voluntary health and welfare organizations but is optional for all others. A public golf course is not a voluntary health and welfare organization.