Nine astronauts, in relays of three, worked in the Skylab earth orbiting space station from May 1973 to February 1974.是什么意思_Nine astronauts, in relays of three, worked in the Skylab earth orbiting space station from May 1973 to February 1974.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句