Section B
Directions: There are 2 passages in this section. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A, B, C and D. You should decide on the best choice.
A massive sandstorm has affected most of northern China, covering the capital Beijing in a dense dust and reducing visibility to less than 50 meters in some areas. The storm is the strongest and most intense this spring, and hit China's north on March with fierce winds.
Sandstorm has posed a serious threat to the air quality and environment. Sandstorms which occurred in ancient times are widely known among in Inner Mongolia as "Huang-mao-feng", meaning "wind that carries yellow sand". In recent years, sandstorms have occurred more frequently, at shorter intervals, and with greater intensity. A sandstorm on Dec. 31st, 2000 was the first one to hit China in decades. From then on, there has been one every month. We cannot help but ask: is this a phenomenon purely powered by Mother Nature, an occurrence over which we have no control？ The fact is that they are caused largely by human actions, mainly excessive use and exploitation of grasslands. Under normal conditions, Inner Mongolia provides grazing for up to some forty million sheep. However, as many as seventy million sheep have been feeding on that area.
With the global climate constantly changing, sandstorms are expected to occur more frequently, and humanity will be forced to confront the delayed effects of the exploited environment. It is only recently that some of us, who have been pursuing economic goal, have begun noticing the environmental problems. Perhaps man, who is finally eating his own bitter fruits, will understand that economic development does not have to be at the expense of the environment. In fact, environmental preservation and economic development should go hand in hand. Take herding for example: enclosed herding is better than open herding for preserving grasslands. Therefore, there are choices that could be made in this respect, with consideration for the preservation of the ecosystem.
According to the passage, what kind of environmental problem will sandstorms bring about？

A. It will turn cities dirtier than they used to be.
B. It wilt make people hard to breathe clean air.
C. It will prevent people finding their direction.
D. It will cause serious air pollution in people's life.