单选题 Sandstorms hit northwestern China's Gansu Province and North China's Inner Mongolia Autonomous Region (内蒙古自治区) on the first day of the new century. According to Sun Landong, a meteorologist with the Lanzhou meteorology Observatory, visibility (能见度) was less than 100 meters in Minqin, a Gansu county near Inner Mongolia, because of sand. When visibility drops to less than 1 kilometer, it is called a sandstorm. The sandstorm in Minqin blew up dust in neighboring towns, such as Baiyu, Wuwei, Jichang and Lanzhou, the capital city of Gansu Province. Dust-laden winds also swept into Beijing. Brought by northwest lies blowing at more than 20 meters per second, dust first reached the capital's the temperature down to as low as 8 below zero and many flights put off their planned time from the city's airport.
It is quite rare for sandstorms, which are frequent between March and June, to happen in winter, when the earth is frozen. The sandstorms in Gansu and Inner Mongolia do not necessarily mean there will be more of them in the spring than last year, when they were serious, but Beijing is taking it very serious. It is reported that Beijing will spend 6 billion Yuan (US $ 725 million)in preventing sandstorms in the capital and has already set up a special team to make sure what causes them.

单选题 What is the main idea of the passage?
A. Sandstorms took place in Gansu.
B. Sandstorms happened on the first day of the new century.
C. Sandstorms are very serious, compared to last year.
D. the experts are trying their best to determine the cause of the sandstorm

单选题 Suppose the dust was 300 kilometers away from Beijing, it would reach Beijing about ______ hours later if it travels at a speed of 20 meters per second?
A. 4.2 B. 15
C. 20 D. 25

单选题 Why did sandstorms begin in the winter this year?
A. Because there was little snow this season.
B. Because a lot of trees have been cut down.
C. Because people took few measures to control them.
D. It is not mentioned in the passage.

单选题 Which of the following doesn't belong to the bad effect the sandstorms have done in Beijing?
A. The temperature fell.
B. Flights put off their time to take off.
C. The air is dirty.
D. People had three days off.

单选题 The author wrote the passage to ______.
A. tell us the environments are becoming worse and worse
B. explain what measures people have taken to control sandstorms
C. make people realize the need to protect the environment
D. call on us to do what we can to save the earth