管管道
- 网络tube
 
管管道管管道
tube
TOEFL+21天 ... truth n 真理;真实;真相,事实 tube n 管,管道;管状地下隧道 tundra n 冻土带,寒漠 ... 
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        Specification for structural design of buried rectangular pipeline of water supply and sewerage engineering
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