TUVALU, a tiny country in the Pacific Ocean, has asked for help as it fears it will be swallowed up by the sea.Storms and huge waves are a constant threat and none of Tuvalu’s nine little islands is more than five meters above sea level, Salt water is already entering the country’s drinking water supply, as well as damaging plants that produce fruit and vegetable. 51
52 . Venice, a historic city in Italy best known for its canals, has sunk about 24 cm over the past 100 years. Experts say that it will have sunk another 20-50cm by 2050. A century ago, St. Mark’s Square, the lowest point in the city, floodedd about nine times a year, Nowadays, it happens more than 100 times. While Venice is slowly sinking into the mud on which it stands, Tuvalu’s rising sea level is caused by global warming.
The average global temperature has increased by almost 0.5 centigrade degrees over the past century; scientists expect it to rise by extra 1-3 degrees over the next 100 years.
Warmer weather makes glaciersmelt, adding more water to the ocean. The warmer temperatures also make water expand, so it takes up more space, causing the sea level to rise. The sea level has risen about 10－25 cm in the last 100 years.
53 . Through burning coal, oil and gas, people have been increasing the greenhouse gases in the atmosphere, such as CO2. This adds to the power of the greenhouse effect, making the planet even warmer.
Many scientists believe that, if the warming is not stopped, there will be huge climate changes. 54 . 55 , the sea will swallow up millions of homes and the world will be flooded with “climate refugees” looking for somewhere to live.A．The main cause of global warming is human pollution B．Should this e true C．Without urgent help, the country’s days are numbered. D．But Tuvalu is not the first place to face sinking into the sea E. The sea level could rise by one meter this century.
F. people face a lot of pollution.
G. much has been done about our planet . C
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(答案→)C
解析：
【小题1】C 根据本段前面内容可知这个国家面临着巨大的威胁，如果没有救助，灭亡之日不远了。
【小题2】D 根据下文提及的威尼斯在过去的100年当中也下沉了很多，说明Tuvalu不是唯一面临危险的国家。
【小题3】A 本段接下来的内容都是讲述的全球变暖的问题，故A正确。
【小题4】Ｅ 根据上文提及如果全球变暖不停止，将会有更大的气候变化，后面接着就应该讲述其中的一个变化，而海平面上升正是其中之一。
【小题5】B 接着上一句，如果海平面上升了一米，海水将会吞没很多地方。那么这是一个虚拟语气，且是与将来相反的虚拟语气，省略了if，句子用倒装的形式。