污水沟位于(),由下倾式内底边板和舭列板围成。
常见于横骨架式双层底结构中的肋板是:() ①、组合肋板;②、舭列板;③、轻型肋板;④、舭肋板
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
下列哪些不是双层底的肋板?() ①、水密肋板;②、箱形肋板;③、舭列板;④、组合肋板
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