杰克: I think the biggest environment problem in my country is air pollution.
凯西: Yes, I agree. The air here is much more polluted than in my country. Of course, my country is more agricultural and has much less industry.
杰克: We have reduced emission of air pollutants in recent years, but cars are still a major source of them. Factories have become cleaner as stricter environment pollution law have been introduced.
凯西: The problem is now on a truly global scale. I don`t believe that any single country can do anything about it.
杰克: I think you`re right. There needs to be an international response to this problem.??