They may be knocking down one or two themselves there, because nobody's paying any attention.

他们中的一两个可能会相互打闹或者摔伤,因为没人照看

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And once upon a time they actually were thinking about knocking it down

从前，人们也想过要拆毁它，

中央车站的历史 - SpeakingMax英语口语达人

It might bend and bow, that is it's not the forces of nature like the movement of the river that's knocking the bridge down, but it's just the failure of these materials over time, that they don't last as long as they might.

这桥可能会折断,不一定是洪水这样的自然灾害,导致了桥梁的坍塌,可能只是因为建桥的材料老化,这种材料没有那么持久耐用

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