[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 US 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 explorers involved all accomplished some significant science simply by going where no scientists had gone.
Today Mars looms as humanity’s next great terra incognita. 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 profits or
A. international cooperation
B. scientific research
C. nationalistic reasons
D. long-term profits

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