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 computer 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.
參考答案：
41 B 該題問(wèn)的是Nyos和Monoun兩湖噴發(fā)時(shí)會(huì)出現(xiàn)什么情況?第一段第五句提到，Monoun噴發(fā)時(shí)有毒氣體隨之而出。兩年后，Nyos湖噴發(fā)時(shí)也出現(xiàn)類似情況。故B為答案。
42 c 本題為細(xì)節(jié)題。問(wèn)的是關(guān)于Nyos和Monoun兩湖哪句陳述是正確的?選項(xiàng)A說(shuō)的是兩湖于1984年形成的，不符合原文意思。選項(xiàng)B的意思是：他們坐落在兩座活活火山上，也與原文意思不符。選項(xiàng)D說(shuō)的是湖中的水定期翻滾，均與原文不符。只有選項(xiàng)c正確。
43 D 題句的意思是：Nyos和Monoun兩湖發(fā)生噴發(fā)的原因是什么?前三個(gè)選項(xiàng)均與原文意思不符，答案見第三段第二句。
44 A 本題問(wèn)的是一隊(duì)科學(xué)家干了什么工作?第四段第三句提到他們?cè)诤锪⒘艘桓尫藕讱鈮旱墓茏印９蔄為答案。
45 c 本題問(wèn)的是在文章最后一段我們了解到了什么?文章最后一段主要講的是在所有的湖里豎起緩解湖底氣壓的管子后，就不會(huì)有危險(xiǎn)。故選項(xiàng)c為正確答案。