2. 职称英语
  3. In 1961, NASA has encouraged studies of space-planes that could be built using e

In 1961, NASA has encouraged studies of space-planes that could be built using e

游客2024-06-17  51
问题 In 1961, NASA has encouraged studies of space-planes that could be built using existing technology. [br] The main difficulties of space flight are neither______ nor______.
选项
答案 technical，commercial
解析 第2段的第l句可以找到答案，要实现这一梦想并不是技术和商业上的问题。
转载请注明原文地址:http://tihaiku.com/zcyy/3637957.html
相关试题推荐
随机试题
最新回复(0)