6.In order to be able to study Earth,the sun,and humans'
问题描述：
6.In order to be able to study Earth,the sun,and humans'
ability to live and work in space,_______________
were developed and launched.
a.Saturn V rockets
b.the Mercury spacecraft
c.space stations
d.starships
答
C
大意是说,为了尽可能研究地球、太阳、以及人们在太空中的工作和生活能力,（空间站）技术被研发并投入使用