20.Scientists in Colombia have trained a team of rats to help remove land mines from the countryside.Land mines are small bombs (炸彈) hidden in the ground and designed to explode when someone steps on them.
When trained,the rats can smell special metals in the mines and then signal to their human team.Then why use rats for such an important job?
In the past,dogs have been used to find bombs.Rats have a good sense of smell and can respond to orders,just like dogs do.But rats are much lighter than dogs.They stand less of a chance of setting off the mines,which explode under a certain amount of weight.What's more,the best rats are cheaper to keep than dogs.It costs about the same amount of money to take care of one dog as it does 70rats.
The rats have already been used in Tanzania,an African country with many land mines.Luisa Fernanda Méndez and her team in Colombia are training the even lighter Wistar rats.These are the white rats with red eyes that scientists often use in laboratory experiments."They even train their babies to perform their jobs,which saves us a lot of time,"Méndez said.
Colombia has the second-highest rate (比率) of deaths from land mine accidents in the world.Last year,land mines killed 695people-56of whom were children.A criminal (犯罪的) group called the Revolutionary Armed Forces of Colombia,or FARC,as well as other organizations,have placed the mines.FARC are strongly against Colombia's government.The group has placed mines all around its own bases and in many places in the countryside.
In the past,the Colombian government hired peasants and poor farmers to find mines.Many of them died trying to find the well-hidden bombs.
Colombian police official Erick Guzmán hopes the team of rats can come to the rescue."These rats will be a great help,"he said.
45.How do rats help to find land mines?A
A.By their sense of smell.
B.By their light weight.
C.By their special sight.
D.By their excellent hearing.
46.The advantage of rats over dogs in finding bombs is thatD.
A.they are cleverer
B.they run faster
C.they have a better sense of smell
D.they don't make mines explode as easily
47.The underlined word"They"may refer toC.
A.dogs
B.scientists
C.Wistar rats
D.Méndez and her team
48.What is the text mainly about?B
A.People in Tanzania are suffering from land mines.
B.Specially-trained rats help clear land mines.
C.Dogs are no longer used to find land mines.
D.Land mines have become a great danger to Colombians.
分析 本文敘述了科學家們在哥倫比亞已經(jīng)訓練一組老鼠幫助在農(nóng)村清除地雷.以前用狗來幫助清除地雷,老鼠的優(yōu)勢是它有靈敏的嗅覺,能夠聞出特殊的金屬味,并且它們的體重輕引爆地雷的可能性小,還有養(yǎng)它們的費用比養(yǎng)狗的費用低.
解答 45.A 細節(jié)理解題.根據(jù)第二段的therats can smell special metals in the mines and then signal(發(fā)信號) to their human team.老鼠可以聞到地雷中的特殊金屬,然后給人發(fā)信號,故選A.
46.D 細節(jié)理解題.根據(jù)第三段的Butrats are much lighter than dogs.They stand less of a chance ofsetting off the mines,但是老鼠比狗更輕.他們的體重輕引爆地雷的可能性小,故選D.
47.C 詞義猜測題.根據(jù)前面的LuisaFernanda Méndez and her team in Colombia are training the even lighter Wistarrats.These are thewhite rats with red eyes that scientists often use in laboratory experiments.Luisa Fernanda Méndez女士和她的團隊在哥倫比亞訓練的更輕的Wistar rats,這些紅眼睛的小白鼠,科學家們經(jīng)常在實驗室做實驗中使用.所以此處指上文提到的Wistar rats,故選C.
48.B 主旨大意題.根據(jù)全文的內(nèi)容可知,主要介紹了受過特殊訓練的老鼠幫助人們清理地雷的事,故選B.
點評 本文是科教類閱讀,主要考查細節(jié)理解題和推理判斷題.在做細節(jié)理解題時,首先根據(jù)題目要求迅速在文章里找出相應的段落、句子或短語.認真比較選項和文中細節(jié)的區(qū)別,在做推理判斷題時不要以個人的主觀想象代替文章的事實,要根據(jù)文章事實進行合乎邏輯的推理判斷.