Sandstorms hit northwestern China's Gansu Province and North China's Inner Mongolia Autonomous Region on the first day this year. According to Sun Landong,a meteorologist with the Lanzhou Meteorology Observatory,visibility 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 Baiyin,Wuwei,Jinchang and Lanzhou,the capital city of Gansu Province Dust-laden winds also swept into Beijing. Brought by northwesterly blowing at more than 20 meters per second, dust first reached the capital's suburbs at 7 a. m.,downtown areas at 9 a. m. The winds,which died down during the night,brought the temperature down to as low as 8 0C 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 seriously. 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. Why did sandstorms begin in the winter this year?
Because there was little snow this season. Because a lot of trees have been cut down. Because people took few measures to control them. It is not mentioned in the passage .
Question: Sandstorms hit northwestern China's Gansu Province and North China's Inner Mongolia Autonomous Region on the first day this year. According to Sun Landong,a meteorologist with the Lanzhou Meteorology Observatory,visibility 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 Baiyin,Wuwei,Jinchang and Lanzhou,the capital city of Gansu Province Dust-laden winds also swept into Beijing. Brought by northwesterly blowing at more than 20 meters per second, dust first reached the capital's suburbs at 7 a. m.,downtown areas at 9 a. m. The winds,which died down during the night,brought the temperature down to as low as 8 0C 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 seriously. 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. 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 .
Answer: