For six months, the astronauts have kept in touch with the research centre on the earth by radio.
For six months, the astronauts have kept in touch with the research centre on the earth by radio.
六个月来，宇航员们一直用无线电与地面上的研究中心保持联系。
For six months, the astronauts have kept in touch with the research centre on the earth by radio.
六个月来，宇航员们一直用无线电与地面上的研究中心保持联系。