Should the U.S. halt human space flight?
　　The Columbia accident has revived the debate on whether the rewards of human space exploration are worth the risks No. I was a teacher when men first landed on the moon in 1969, and I remember how it moved my students and this country.__________(46) And we haven't ventured outward since then. That's 30 years too long! America's human space-flight program is adrift, with no clear vision or goals beyond the completion of the International Space Station.采集者退散
　　I want NASA to establish a phased series of goals over the next 20 years, including human visits to asteroids that cross the Earth's orbit, establishing a research and living facility for humans on the moon, and human expeditions to the surface of. Mars and its moons.__________(47)
　　An astronaut is today's Christopher Columbus, who sailed into the unknown and discovered the Americas. The knowledge we gain from having actual people exploring can never be replaced by robots.__________(48) Robots are useful, but humans can do things that robots can't.
　　The real obstacle we face in overcoming the drift in the nation's human space-flight program is not technological and it's not financial.__________(49)
　　The lesson from the Columbia accident is not that humans don't belong in space. ______(50)
　　A Instead, we should honor the memory of the lost astronauts by pushing our exploration of space future.
　　B Astronauts are key to this expanded exploration.
　　C It's the lack of commitment to get started.
　　D Until then, we should stop risking people's lives by sending them into space.
　　E It is now more than 30 years since the last American left the surface of the moon and returned to Earth.
　　F Our ability to send humans into space and have them return gives us amazing information about ourselves and our universe.
　　答案：E B F C A