2. 外语
  3. A project likely to evolve in the near or intermediate future is space tourism. Today space tourism has become a pure commercial

A project likely to evolve in the near or intermediate future is space tourism. Today space tourism has become a pure commercial

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问题     A project likely to evolve in the near or intermediate future is space
tourism. Today space tourism has become a pure commercial activity【S1】________
that would not have to rely unpredictable government decisions. It would【S2】________
therefore put space operations on a much more solid, dependable footing
and would enormously expand man’s space activity. If some people see【S3】________
space tourism as a potential multibillion—dollar business, difficult
technical problems remain to be solved.
    First, in order to fulfill the dream of space tourism, a manned
reusable rocket like the Venture Star must be built. Then, the second【S4】________
serious problem must be addressed：Even today’s most—advanced space
rockets are able to lift only about 2. 5％of their launch weight into
0rbit—a ratio that has hardly changed in the last 40 years. But it is【S5】________
simply impossible to find other alternations other than a rocket. This【S6】________
unsatisfying fact is a result of the limits of material characteristics and
chemical power sources, and there is no indication which any【S7】________
fundamental breakthrough call be expected in these areas in the
foreseeable future. Then these who have long-cherished dreams of space【S8】________
tourism have to Wait forever.
    Operational costs may be somewhat reduced by the use of air-
breathing engines to help a reusable rocket penetrate into the earth’s
atmosphere. Today the highest cost attainable to lift a payload into orbit【S9】________
is more than$4, 000 per pound；the price of a ticket to space would
have to be at least$50. 000. It is questionable whether a sufficient
number of customers could be tempted to pay SO a high price for a short【S10】________
trip around the world.  
【S5】
选项
答案But—And
解析 连词误用。上文指出“即使是今天最先进的火箭，进入轨道的最大承重力也只是它自身重力的2．5％，这一点40年来一直没有突破”，本句指出“人们除了火箭之外又找不到可以替代的东西”，可见二者是递进关系，而不是转折关系。
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