[单项选择]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 Apollo astronauts rocketed to the moon in a dramatic show off technological muscle during the cold war.
Although their missions blended commercial and political-military imperatives, the explorers involved all accomplished some significant science simply by going where no scientists had gone before.
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 ventures, it is clear that imperatives other than prof
A. make clear the complex chemistry in the development of life
B. confirm the suggestion that bacterial fossils traveled to Earth on a meteor
C. reveal the kind of conditions under which life originates
D. provide an explanation why life is common in the universe

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