The Exploding Lakes of Cameroon
Lake Nyos and Lake Monoun are craterlakes They were formed when water collected in the craters of old volcanoes The volcanoes under Lake Nyos and Lake Monoun are not active anymore. However, poisonous gases from the center of the earth continue to flow up through cracks in the bottom of the lake. This is normal in a crater lake. In most crater lakes，these gases are released often because the waterturns overregularly.That is，the water from the bottom of the lake rises and mixes with the water at the top，allowing the gases to escape slowly.
In the past，no one knew when the gases might explode，so there was no way for the villagers to escape disaster. Now scientists from the United States，France，and Cameroon have found a way to reduce the gas pressure at the bottom of Lake Nyos.They stood a 672-foot plastic pipe in the middle of the lake，with one end of the pipe near the bottom and the other end in the air.Near the top of the pipe，the team put several holes that could be opened or closed by a computer.Now，when the gas pressure gets too high，the holes are opened and some of the gas-filled water shoots up through the pipe into the air like a fountain.With less pressure，a disastrous explosion is much less likely.However, the scientists are not sure that one pipe will be enough to prevent explosions.They hope to put in others soon and they plan to install a similar pipe and a computer system at Lake Monoun as well.
41 What will happen when Lake Nyos and Lake Monoun explode?
B Poisonous gases will be released suddenly.
D The volcanoes will come to life.
A They were formed in 1984.
C They are not like most other crater lakes.
43 Lake Nyos and Lake Monoun explode because
B people from the villages turn over the water.
D they have more gases trapped at the bottom than other crater lakes
A erected a pressure-releasing pipe in the lake
C built a beautiful fountain near the lakes
45 What do we learn from the last paragraph?
B Scientists still do not know how to prevent gas explosions
D Warning systems have been set up in the villages nearby.
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。
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。
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。