单项选择题
A．keeps himself from using its benefits B．cannot enjoy its benefits at any time C．fails to keep its benefits from being used D．enjoy its benefits all the same
A．there will be no safety if there is no national defense B．all the people should be responsible for national defense C．a public good is a shared benefit for the whole society D．some public goods are more important than others
A．book adventure film tickets B．arrange for a special activity C．ask for reduced charges D．seek more information on Arboretum