题目内容：

Almost a seventh of China has been under heavy smog. The air pollution in 20 cities has reached the “danger level”. China is not alone, however. Many countries have the same situation. The air pollution is a problem from which we can't hide.

The United States

Since the beginning of the 19th century, America has had trouble with environmental problems, air pollution in particular. Almost 60 percent of Americans live in areas, where air pollution has reached unhealthy levels. It can make people sick.

The US created the Environmental Protection Agency in 1970 and passed the Clean Air Act. Now the air  all over the country is much cleaner, especially compared to ten years ago.

London

Yellow­grey smog was a frequent visitor to London in the 1950s and got the name “London fog”. The heaviest, which shocked the world, was in 1952. Because of cold weather and windless conditions, polluted air covered the city. People could see something around them only in a few meters and about 4，000 people died. In 1956, London passed the Clean Air Act. It largely reduced air pollution.

New Delhi

Because New Delhi is developing fast, its air quality is even worse than that of Chinese cities. New Delhi has done little to improve air quality in recent years. However, the city government made a few changes more than 10 years ago. They moved industry out of the city, built a subway and improved public transport.

根据短文内容，完成下面的表格。

World Battles Against Air Pollution
China	As for the air pollution, China is not 1.； many countries have the same situation.
The United States	About 60 percent of Americans live in areas, where 2. has reached unhealthy levels. The Environmental Protection Agency 3. by the US in 1970.
London	In 1952, the 4. smog shocked the world.
New Delhi	Because New Delhi is developing fast, its air quality is even 5. than that of Chinese cities.