单项选择题
A．not something anyone wants to run. B．the responsibility of the government. C．administered by private doctors. D．handled adequately by travel agents.
A．car causes pollution only in some cities. B．60% of the cities are affected by car pollution. C．90% of the city residents suffer from car pollution. D．car is the main contributing factor in polluting air.
A．a newspaper. B．the government. C．a construction firm. D．a private company.