Passage Four Questions 35 to 40 are based on the following passage.
For centuries, explorers have risked their lives venturing into the unknown for reasons that were to varying degrees economic and nationalistic. Columbus went west to look for better trade routes to the Orient and to promote the greater glory of Spain. Lewis and Clark journeyed into the American wilderness to find out what the U.S. had acquired when it purchased Louisiana, and the Appolo astronauts rocketed to the moon in a dramatic show of technological muscle during the cold war.
Although their missions blended commercial and political-military imperatives,the explorerss involved all accomplished some singificant science simply by going where no scientists had gone.
Today Mars looms(隐约出现)as humanity's next great terra incognita(未探明之地).And with doubtful prospects for a short-term financial return,with the cold war a rapidly fading memory and amid a growing emphasis on international cooperation in large space ventues,it is clear that imperatives other than profits or nationalism will have to compel human beings to leave their 's reddish surfface.Could it be that science,which has long played a minor role in exploration,is at last destined to take a leading role? The question naturally invites a couple of others:Are there experiments that only humans could do on Mars? Could those experiments provide insights profound enough to justify the expense of sending people across in terplanetary space?
With Mars the scientific stakes are arguably higher than they have ever been.The issue of whether life ever existed on the planet, and whether it persists to this day,has been highlighted by mounting evidence that the Red Planet had abundant stable,liquid water and by the continuing controversy over suggestions that bacterial fossils rode to Earth on a meteorite(陨石)from Mars .A more conclusive answer about life on Mars ,past or present ,would give researchers invaluable data about the range of conditions under which a planet can chemistry that leads to life.If it could be established that life arose independently on Mars and Earth ,the finding would provide the first concrete clues in one deepest mysteries in all of science:the prevalence of life in the universe.
36.According to the passage,the chief purpose of explorers in going to unknown places in the past was _______. A)to display their country's military might B)to accomplish some significant science C)to find new areas for colonization D)to pursue commercial and state interests
37.At present ,a probable inducement for countries to initiate large-scale space ventures is _______. A)International cooperation B)scientific research C)nationalistic reasons D)long-term profits
38.What is the main goal of sending human missions to Mars? A)To find out if life ever existed there. B)To see if humans could survive there. C)To prove the feasibiliy of large-scale space ventures. D)To show the leading role of science in space exploration
39.By saying"With Mars the scientific stakes are arguably higher than they have ever been"(Line 1,Para .4),the author means that ______. A)with Mars the risks involved are much greater than any previous space ventures B)in the case of Mars ,the rewards of scientific exploration can be very high C)in the case of Mars,much more research funds are needed than ever before D)with Mars ,scientists argue ,the fundamental interests of science are at issue
40.The passage tells us that proof of life on Mars would _______. A)make clear the complex chemistry in the development of life B)confirm the suggestion that bacterial fossils travelled to Earth on a meteorite C)reveal the kind of conditions under which life originates D)provide an explanation why life is common in the universe
's reddish surfface.Could it be that science,which has long played a minor role in exploration,is at last destined to take a leading role? The question naturally invites a couple of others:Are there experiments that only humans could do on Mars? Could those experiments provide insights profound enough to justify the expense of sending people across in terplanetary space? 
chemistry that leads to life.If it could be established that life arose independently on Mars and Earth ,the finding would provide the first concrete clues in one deepest mysteries in all of science:the prevalence of life in the universe. 
