Avalanches (雪崩) are one of those natural disasters that can cause great damage and only Mother Nature knows when and where they're going to occur. Even with modern technology it's still impossible to know exactly when or where one is going to occur. Mountain climbers are wise to be careful, as avalanches kill many of them each year.
The physics of how and why an avalanche occurs is complex. There are times of higher probability. During the year, the transition from winter to spring will cause some snow and ice to melt, which may trigger avalanches. Also at daybreak there is a higher probability due to the temperature change.
While climbers hike up slopes (斜坡), some distance between the climbers should be kept. If an avalanche occurs, then there will be fewer lives lost and a higher probability that someone will be able to seek help. Since an accident is more likely to happen when a top layer of snow is loose, avoid areas where heavy snow or rain has recently occurred.
Try to choose areas that you are familiar with and stay in areas with rocks, bushes and trees. Trees and bushes allow snow to pile up and keep the layers stable (稳定的). If an avalanche occurs, trees will take the impact of the snow, so there is a better chance of being safe.
Climbers must also pay attention to the degree of the slope. Avalanches won't occur on level ground and there is little snowfall on very steep areas. The greatest danger is in areas where the slope is between 25 and 40 degrees.
Remember that, if you get stuck in an avalanche, there is no car hire available to take you to the nearest airport.
1．What do we know from the first paragraph?
A. Many mountain climbers die of avalanches each year.
B. Of all the natural disasters, avalanches cause the greatest damage.
C. Most climbers who meet avalanches die for not paying enough attention to avalanches.
D. With the development of science and technology, avalanches can now be predicted exactly.
答案与解析 A 细节理解题。根据第一段“avalanches kill many of them each year”可知A项正确。
2．The underlined word “trigger” in the second paragraph probably means “________”．
A. make use of B. result in
C. put an end to D. slow down
答案与解析 B 词义猜测题。第二段主要讲雪崩多发的时间，故可以判断冬春季节交替时引起的雪和冰的融化会导致雪崩的发生。
3．Why is there a higher probability that an avalanche occurs at daybreak?
A. Because daybreak is the coldest time of the day in the mountains.
B. Because it often snows heavily in the mountains at daybreak.
C. Because temperature changes at daybreak.
D. Because the top layer snow is loose at daybreak.
答案与解析 C 细节理解题。根据第二段“Also at daybreak there is a higher probability due to the temperature change”可知C项正确。
4．It wouldn't be a good idea for a climber to ________ while climbing a mountain.
A. keep some distance from other climbers
B. avoid areas where heavy snow or rain has recently occurred
C. choose areas that he or she is familiar with
D. climb up a slope which is between 25 and 40 degrees
答案与解析 D 细节理解题。根据第五段“The greatest danger is in areas where the slope is between 25 and 40 degrees.”可知，25度到40度之间的斜坡是最危险的，故选D项。
