There exist three ways which are chronological-flashback-patching in terms of narrative time, and two structural forms, interior and exterior, in terms of narrative space.

在叙事时间上，有顺———倒———补三种形态。在叙事空间上，有内部与外部两种结构形式。

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Two structural forms can change under pressure to realize a water supply and drainage function of automatic quantify for a single opening.

两种结构形式均可依靠压力的变化，实现单口自动定量给排水功能。

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There are many types of sulfide minerals, but pyrite and marcasite, the two structural forms of FeS2 that are especially common in coal regions, are the major acid-producers.

FORBES: Fracking With Bad Water