To protect people nearby until all of the pipes are in place．the scientists have installed early
warning systems at both lakes. If the gas pressure rises to a dangerous level，#puters will set
off loud sirens(警报)and bright lights to warn the people in the villages．That way, they will
have time to escape from the dangerous gases．
41 What will happen when Lake Nyos and Lake Monoun explode?
A Water will flow down the hills
B Poisonous gases will be released suddenly．
C A strong wind will rise from the lakes
D The volcanoes will #e to life．
42 Which of the following statements about Lake Nyos and Lake Monoun is true?
A They were formed in 1984．
B They are at the top of two active volcanoes．
C They are not like most other crater lakes．
D Water in them turns over regularly．
43 Lake Nyos and Lake Monoun explode because
A the gases rise to the top and mix with air．
B people from the villages turn over the water．
C scientists have put in a #puter system．
D they have more gases trapped at the bottom than other crater lakes
44 A team of scientists has
A erected a pressure-releasing pipe in the lake
B identified the gases at the bottom of the lake
C built a beautiful fountain near the lakes
D removed all dangerous gases from the lakes
45 What do we learn from the last paragraph?
A Scientists are planning to install pipes in all crater lakes．
B Scientists still do not know how to prevent gas explosions
C Explosion disasters could be avoided in the future
D Warning systems have been set up in the villages nearby．
参考答案：
41 B 该题问的是Nyos和Monoun两湖喷发时会出现什么情况?第一段第五句提
到，Monoun喷发时有毒气体随之而出。两年后，Nyos湖喷发时也出现类似情况。
故B为答案。
42 c 本题为细节题。问的是关于Nyos和Monoun两湖哪句陈述是正确的?选项A
说的是两湖于1984年形成的，不符合原文意思。选项B的意思是：他们坐落在两
座活活火山上，也与原文意思不符。选项D说的是湖中的水定期翻滚，均与原文
不符。只有选项c正确。
43 D 题句的意思是：Nyos和Monoun两湖发生喷发的原因是什么?前三个选项均
与原文意思不符，答案见第三段第二句。
44 A 本题问的是一队科学家干了什么工作?第四段第三句提到他们在湖里立了一
根释放湖底气压的管子。故A为答案。
45 c 本题问的是在文章最后一段我们了解到了什么?文章最后一段主要讲的是在
所有的湖里竖起缓解湖底气压的管子后，就不会有危险。故选项c为正确答案
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