There are many research stations on the earth outer space is studied. [ ] A．in w
来源：网络
时间：
推荐文章
![There are many research stations on the earth outer space is studied. [ ] A．in w](/pic/43_744689.jpg)
There are many research stations on the earth ________ outer space is studied.
[]
A．in whichB．on them
试题答案
答案：A
There are many research stations on the earth ________ outer space is studied.
[]
A．in whichB．on them
答案：A