1．For more than twenty years scientists have been searching for signs of life on other planets．Most of these searches have been done over the radio．The hope is that someone in outer space may be trying to get in touch with us．Scientists also have sent radio and television messages on spaceships traveling through space，on the chance that someone may be receptive to such messages．
Scientists are using powerful radio telescopes to listen to signals from about 1，000stars，all within 100light years of earth．In addition，they will scan the entire sky to"listen"for radio messages from more distant stars．Using a computer，they will be able to monitor more than eight channels at one time．Scientists are looking for any signal they stands out from the background noise．
Of the 200billion stars in the Milky Way galaxy，scientists find that five percent are like our sun．Perhaps half of them have a planet like earth．Such a planet would be a reasonable distance from the star for temperatures to be right for the evolution of life．Based on the inhabitable（that can be lived in）planets in our galaxy，most scientists agree that chances are likely that one or more of these planets support some life．
However，many scientists wonder whether intelligent life exists on other planets．Some believe that twenty years of searching without any intelligible messages shows that no one is out there．They say that the evolution of intelligence comparable to ours is unlikely．
Other scientists believe that our search hasn't been long enough to rule out the possibility that intelligent life exists in our galaxy．Although our sun family is only about five billion years old，our galaxy is about 20billion years old．In that time，some scientists think it is likely that civilization much more advanced than ours have developed．Perhaps these civilizations send us no signals； perhaps we have not recognized the signals they have sent us．If we hope to find intelligent life，these scientists believe that we have to keep looking．
29．According to the passage，how many planets in our galaxy might be inhabitable？A
A.5billion．
B.10billion．
C.15billion．
D.200billion
30．The first paragraph in this passage is mainly aboutA．
A．how scientists are looking for signs of life on other planets
B．why scientists are looking for signs of life on other planets
C．where scientists are looking for signs of life on other planets
D．when scientists are looking for signs of life on other planets
31．The underlined word"monitor"in the passage means"C"．
A．find
B．imitate
C．check
D．form
32．Which of these statements is true based on the information in the passage？C
A．The earth is one of the oldest planets in our galaxy．
B．Most scientists believe that there is intelligent life on other planets．
C．Scientists are trying different ways to find signs of life on other planets．
D．Scientists don't believe that there might be life on other planets．
分析 本文討論了人們對于外太空是否存在生命，至今為止，科學家們嘗試了多種方法尋找外星生命，但都沒有得到回應(yīng)．也有科學家認為外太空不太可能存在生命．
解答 29．A 推理判斷題．根據(jù)第三段前兩句 Of the 200 billion stars in the Milky Way galaxy，scientists find that five percent are like our sun．Perhaps half of them have a planet like earth．可知在銀河系里有200billion顆恒星，其中百分之五的恒星有一顆像地球這樣的行星．那么也就是10billion顆諸如地球的行星．故A正確．
30．A 段落大意題．根據(jù)本段第二句Most of these searches have been done over the radio．和最后一句Scientists also have sent radio and television messages on spaceships traveling through space，on the chance that someone may be receptive to such messages．可知本段主要介紹的科學家們通過向太空發(fā)送無線電信號的方式來尋找外星生命．故A項正確．
31．C詞義猜測題．根據(jù)本句Using a computer，they will be able to monitor more than eight channels at one time．科學家們向太空發(fā)射無線電信號以后，使用計算機對這些信號進行監(jiān)控，希望能夠捕捉到外星生命的痕跡．所以該詞意為"check"，故C項正確．
32．C細節(jié)理解題．根據(jù)文章第一段Most of these searches have been done over the radio．Scientists also have sent radio and television messages on spaceships traveling through space，on the chance that someone may be receptive to such messages．可知科學家正在使用多種方法研究外星生命的存在．故C項正確．
點評 本文是一個科教類閱讀理解，題目涉及多道細節(jié)理解題，做題時結(jié)合原文和題目有針對性的找出相關(guān)語句進行仔細分析，結(jié)合選項選出正確答案．推理判斷題也是要在抓住關(guān)鍵句子的基礎(chǔ)上合理的分析才能得出正確答案，切忌胡亂猜測，一定要做到有理有據(jù)．
