13．Now scientists believe that global warming affects hibernating animals，causing them to wake up earlier．While this may seem a little concern，it is in fact a serious environmental problem．The shortened hibernation period could actually lead to significant decreases in the population of several species．
Some of the first evidence of the problem came from Colorado，where researchers at the Rocky Mountain Biological Lab have been observing marmot （旱獺） hibernation behavior since the 1970s．In the early days of their studies，marmots generally hibernated several weeks into the month of May．Nowadays，however，temperatures in the area have risen by 2.5degrees Fahrenheit，and the marmots wake up about a month earlier．
At least the marmots are still hibernating．Several other animals have not been hibernating at all recently．Brown bears in the Spanish Cantabrian Mountains did not hibernate last year．Chipmunks （花鼠） in the US and some snakes in Australia also skipped the hibernation period．The bears seem to have survived without losing many individuals．The chipmunks and snakes，however，were not so lucky．Many of the animals died of starvation during the winter．
The problem with animals waking up early，or skipping hibernation altogether，lies with the creatures'metabolism （新陳代謝）．When the animals hibernate，their metabolism drops significantly．The animals'heart rate slows，and they require very little energy to live．When the animals awake in the spring，their metabolism returns to normal．
But while their metabolism may be as active as it was before hibernation，food sources aren't as available as they were before．A marmot may wake up when temperatures get warmer，thinking it's spring，but plants will not have got the amount of sun they need to grow．So until the plants grow，the marmots have no reliable food source．
Many scientists believe the problem will continue to get worse．For many biologists，that's a scary prospect．Terry Root，an animal expert at Stanford University，said，"I do think what we will be facing is the extinction of many species．"
28．What is the viewpoint of the writer？B
A．Global warming will continue to get worse as time goes on．
B．Waking up early in spring may lead to the extinction of some animals．
C．Shortened hibernation will definitely decrease the population of animals．
D．Animals which do not hibernate die of starvation．
29．The writer sets the example of the marmot in order toA．
A．indicate that global warming influences animals'hibernation
B．explain that the weather gets warmer and warmer now
C．show that the weather in the United States is quite different
D．say some animals do not hibernate now due to warm weather
30．Judging from recent observation，which of the following animals suffered the LEAST from shortened hibernation？A
A．Brown bears．
B．Marmots．
C．Some snakes in Australia．
D．Chipmunks in the US．
31．Why can't marmots find enough food when they wake up？D
A．Because there are too many marmots in the wild now．
B．Because more and more animal species skip hibernation now．
C．Because winter days end much earlier than before．
D．Because plants haven't received enough sunlight for spring growth．
分析 本文屬于說明文閱讀，作者通過這篇文章主要向我們描述了全球變暖帶來的連鎖反應(yīng)很多，其中之一就是導(dǎo)致一些冬眠的動物的冬眠期變短，給這些動物帶來巨大的影響；
解答 28．B．細(xì)節(jié)理解題．根據(jù)第一段The shortened hibernation period could actually lead to significant decreases in the population of several species．可知冬眠期的縮短導(dǎo)致數(shù)量的減少，故選B項(xiàng)．
29．A．細(xì)節(jié)理解題．根據(jù)第二段Nowadays，however，temperatures in the area have risen by 2.5 degreesFahrenheit，and the marmots wake up about a month earlier．可知作者借這個例子來說明全球變暖使得動物的冬眠期減少，故選A項(xiàng)．
30．A．細(xì)節(jié)理解題．根據(jù)第三段提到Brown bears in the Spanish Cantabrian Mountains did not hibernatelast year可知棕熊去年就沒有冬眠，可知選A項(xiàng)．
34．D．細(xì)節(jié)理解題．根據(jù)倒數(shù)第二段提到but plants will not have got the amount of sun they need to grow．植物沒有得到足夠的陽光來生長，故選D項(xiàng)．
點(diǎn)評 考察學(xué)生的細(xì)節(jié)理解和推理判斷能力，做細(xì)節(jié)理解題時(shí)一定要找到文章中的原句，和題干進(jìn)行比較，再做出正確的選擇．在做推理判斷題不要以個人的主觀想象代替文章的事實(shí)，要根據(jù)文章事實(shí)進(jìn)行合乎邏輯的推理判斷．
