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        1. Scientists overcame (克服) much difficulty they had _____ that technological problem _____ they finally
          could send the manned (載人的) spaceship up into space.

          A. to solve; until
          B. solving; before
          C. to solve; before
          D. solving; until
          B
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          科目:高中英語 來源:期中題 題型:單選題

          Scientists overcame (克服) much difficulty they had _____ that technological problem _____ they finally
          could send the manned (載人的) spaceship up into space.
          [     ]
          A. to solve; until
          B. solving; before
          C. to solve; before
          D. solving; until

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