4.Why is the conquest of space more than a great a [A]Becauseitisfullofchallengesforhumanbeings.[B]Becauseitmaybenecessaryforhumanbeingstosurvive.[C]Becauseitisthegreatestadventureinhumanhistory.[D]Becauseitismoreexcitingthananyotheradventures. 参考答案 查看答案