单项选择题
A．research and development of new medicine B．new devices of prevention C．separation of infectors D．surveillance and information exchange
A．There is no effective way of treating it. B．It may spread quickly among birds and poultry. C．It may affect the world economy and politics. D．It may change to an epidemic among human beings.
A．close their stores B．resort to legal action C．take on a strike D．take some violent actions