2-- They must have just come back from tomb sweeping because today is Tomb Sweeping Day.

1-- Tomb Sweeping Day? What is it?

2-- Tomb Sweeping Day is a traditional festival in China, on which many Chinese mourn the dead.

1-- What do they do?

2-- People go to the cemetery to pay their respects to the dead.

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注解：
 
1.tomb sweeping扫墓 
2.traditional传统的  
3.mourn哀悼   

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译文：

1--那些人怎么都哭了？

2--他们准是刚扫墓回来，因为今天是清明节。

1--清明节？那是什么？

2--清明节是中国的传统节日，在这天中国人要祭奠死者。

1--他们都做什么？

2--他们去墓地。向已故家人表达敬意。