2．Lichens （地衣） are difficult to see．They don't move．They often mix into the living place．You might not even recognize one if you are looking right at it．
Lichens live on rocks，branches，houses，and even metal street signs．You can find these colorful organisms （微生物） almost everywhere-from deserts to rainforests，and from Antarctica to Africa．They've traveled in outer space，and some scientists think there might even be lichens on Mars．
What you probably don't realize is that a lichen is more than a single thing．It includes two different types of living organisms：a fungus （菌類） and an alga （藻類）．Neither of these organisms is a plant，so the lichen isn't a plant either．
Through photosynthesis （光合作用），the alga gets the sun's energy to make food for the fungus，which is the place for the alga to live in．However，the alga cannot leave the fungus．
Around the world，scientists have found tens of thousands of types of lichens．Many may not even have been discovered yet．As scientists continue to find new kinds of lichens，they are also working to understand how they are connected to one another．By putting together a lichen family tree，they hope to understand why so many different types of lichens have grown in so many places around the world．
Many researchers are trying to understand basic facts about the organisms and their connections．Researchers are also using lichens to examine the health of the environment．
56．What do we know about lichens according to the passage？C
A．They will die if they leave Earth．
B．There are more lichens than plants on Earth．
C．They look similar to the environment around them．
D．They are too small to be easily seen by people．
57．What does the second paragraph mainly talk about？B
A．The way lichens live．
B．The natural environment of lichens．
C．The way lichens work as organisms．
D．The family tree of lichens．
58．What is the function of the alga in lichens？B
A．It produces food for the fungus．
B．It offers a living place for the fungus．
C．It makes the lichen a plant．
D．It can protect the fungus．
59．Which of the following statements is NOT the scientists'purposes of studying lichens？C
A．To understand basic facts about them．
B．To create a lichen family tree．
C．To understand how lichens are related to each other．
D．To understand why lichens can live in different places．
60．We can know from the passage thatA．
A．lichens can be used to better understand the environment
B．lichens don't have any differences in colors or sizes
C．lichens don't use photosynthesis like a green plant
D．scientists have discovered every kind of lichen．
分析 文章為科教類，主要介紹了地衣的有關(guān)知識(shí)，并介紹了研究人員想利用地衣來研究環(huán)保．
解答 CBBCA
56．C 細(xì)節(jié)題．根據(jù)第一段They often mix into the living place．You might not even recognize one if you are looking right at it．可知，地衣通常和活生物混在一起，即使你發(fā)現(xiàn)了也不一定認(rèn)出來，所以地衣和周圍的環(huán)境看起來很相似，故答案為C．
57．B 主旨?xì)w納．第二段介紹了地衣主要生長在巖石、樹枝等地方，從沙漠到熱帶雨林都有地衣，概括為重點(diǎn)介紹地衣的生長自然環(huán)境，故答案為B．
58．B 細(xì)節(jié)題．根據(jù)the alga gets the sun's energy to make food for the fungus可知，藻類吸收陽光給菌類提供食物，故答案為B．
59．C 細(xì)節(jié)歸納題．根據(jù)最后兩段的介紹可知，科學(xué)家研究地衣目的有：understand basic facts about the organisms 弄清有機(jī)物基本事實(shí)；By putting together a lichen family tree創(chuàng)造一個(gè)地衣家族系列；why so many different types of lichens have grown in so many places around the world為什么地衣會(huì)生長在不同地方．只有選項(xiàng)C沒有提到，故答案為C．
60．A歸納推理．根據(jù)最后一句話Researchers are also using lichens to examine the health of the environment．可知，研究人員利用地衣來研究環(huán)境的問題，故答案為A．
點(diǎn)評(píng) 本文是一篇科教類閱讀，題目涉及多道主旨大意題，推理判斷題．做題時(shí)學(xué)生應(yīng)仔細(xì)閱讀原文，把握文章主要內(nèi)容，聯(lián)系文章上下文內(nèi)容并結(jié)合所給選項(xiàng)含義，從中選出正確答案，一定要做到有理有據(jù)，切忌胡亂猜測(cè)．
