Let's think about how we can classify single and double and triple bonds,.

我们来考虑一下如何划分单键、双键和三键。

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Whether a single, double, triple or multiple entry visa is required ?

需要一次、两次、三次或多次签证？

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Whether a single, double, triple or multiple entry visa is required ?

需要一次、两次、三次或多次签证？

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