2. 外语
  3. A. attempt B. charged C. crucial D. delicate E. essentially F. eventually G. expended H. fraction I. individual J. maintain

A. attempt B. charged C. crucial D. delicate E. essentially F. eventually G. expended H. fraction I. individual J. maintain

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问题    A. attempt B. charged C. crucial D. delicate E. essentially
   F. eventually G. expended H. fraction I. individual J. maintain
   K. minority L. negligible M. scrapping N. slashing O. upsurging
   Space X launched a cheaper, partially-used rocket into orbit. That’s a stride toward 【C1】______the price tag of sending payload to space. Successfully flying reusable rockets is a 【C2】______step toward the dream of sending people to Mars. Until now, rockets have almost all been single-use. Once the fuel is【C3】______, a rocket stage plummets to Earth, resulting in the destruction of extremely expensive equipment that costs tens of millions of dollars to build.
   Its founder has likened that to 【C4】______a 747 jet after one flight, which would make air travel impossibly expensive. He has suggested that rocket launches could 【C5】______be much cheaper since the cost of the rocket propellants are less than 1 percent of the full-price ticket for a launch. So, if a rocket could be simply refueled like a jetliner for another flight, the cost of space travel could drop to a 【C6】______of what it is now. The stresses of spaceflight on reused boosters, however, are much greater than those on jetliners. The economics will depend on how many times a booster can be flown, and how much the 【C7】______expense will be to repair the booster each time.
   Reusable spaceships are not a new idea. NASA’s space shuttles were the first real 【C8】______at a reusable spaceship, but the shuttles proved more 【C9】______than hoped, requiring an army of technicians to 【C10】______them between flights. As a result, they ended up being more expensive than expendable rockets.
【C2】
选项
答案C
解析 空格前为不定冠词a，空格后为名词step，因此，空格处应填入一个形容词作定语修饰step。空格后提到，将人类送上火星是一个梦想，因此，能够成功地发射可重复使用的火箭是朝着这个梦想迈出的关键一步，故C项crucial“至关重要的，关键性的”为答案。
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