Until this week Saturn's small moon Rhea was the only known solid space object thought to have a ring. (Other known ringed bodies, such as Saturn, are mainly gaseous.)
直到本周土星的小卫星土卫五还被认为是唯一具有环的立体空间物体。(其它已知有环的天体，例如土星，大部分是气态的。)
Design a systematic second-floor pedestrian system, the connection of the solid space should be stated clearly to indicate construction details for lower level.
建立系统有效的二层步行系统，清晰表达立体空间的连接关系，以指导下层次详细工程设计与建设实施。
Design a systematic second-floor pedestrian system, the connection of the solid space should be stated clearly to indicate construction details for lower level.
建立系统有效的二层步行系统，清晰表达立体空间的连接关系，以指导下层次详细工程设计与建设实施。
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