填空题

The main difficulties of space flight are neither______ nor______.

【参考答案】

technical，commercial
<上一题 目录 下一题>
热门 试题

填空题
______ countries have worked together to build the International Space Station.
填空题
British companies have proposed designs that are more suitable than the X - 33 and X - 34, but the government does not support it.
相关试题