Which of the following would best minimize the role air travel can play in the spread of influenza during a pandemic? A. Installing air filtration systems in the planes to kill any flu virus particles flowing through the filters. B. Requiring air travelers to receive flu vaccinations far enough in advance of the trip to provide protection against the disease. C. Refusing to allow children, the elderly, or others who are especially vulnerable to flu to travel by air during a pandemic. D. Requiring all air travelers to wash their hands before boarding a plane. E. Conducting medical examinations during the boarding process to weed out passengers with flu symptoms.