We recently read a report on China's environmental problems, based on reports from Singapore's Straits Times. There was one statistic that shocked us. Environmental experts claim that without some great change, pollution might, within five years, make the Yangtze River just about unsuitable for all forms of life to live in. The baiji, or the Yangtze River dolphin, was only the latest victim. According to the first report, in the 1980s there were 126 forms of life in the river, and by 2002, that figure was already down to 52.    Just how bad is the situation? The Yangtze River flows by 186 cities on its way from Qinghai to Shanghai, and in the process picks up 40% of China's polluted waste water. According to another report, in 2006, China produced a total of 53.7 billion tons of waste water. But that's not the worst news. By 2030, China might possibly use up between 89-100% of its sources of drinking water.    All of this begs a deeper question: What kind of water are they using when they pump 10 kilos of water into pigs headed for the slaughterhouse ? This is an important question because if its waste water is not fit for human to drink, there's a chance that some of whatever was in that water was in the pork you had for lunch today. And if the water is safe to drink, that's a waste of perfectly good water.    Another report we read, related to the Taihu algae  blooming that has left 3 million people in the Wuxi area without drinking water, claims(quite believably) that Taihu's environmental problems will never end until all the factories along the lake close down. The algae bloom is so bad there that lots of people have to take the algae out of the lake all day long instead of fishing. Which of the following problems is the most important according to the passage?
There is no clean water to pump into pigs which are to be slaughtered. A large amount of waste water is produced every year in China. The sources of drinking water might be almost used up in the future. There are poisonous things in the pork that people eat.