復數代詞they, them, their 可以表示單數意義嗎

在通常情況下，復數代詞they, them, their 表示復數意義。如：

As is usual with children, they soon got tired. 孩子們一貫如此, 他們很快就厭倦了。

Although they are twins, they look entirely different. 他們雖是孿生，但是相貌卻完全不同。

If the trees had been given more attention, they could be grown better. 要是對這些樹多加注意，它們會長得更好些。

When guests leave the host usually sees them out. 客人走時，主人通常送出門。

We invited 12, but only a handful of them came. 我們邀請12人，但只有幾個人來。

The Irish are very proud of their sense of humour. 愛爾蘭人為自己的幽默感而自豪。

Most of the families have modernized their kitchens. 大多數家庭已實現廚房設備現代化。

但是，在實際運用中，有時也可以用復數代詞they, them, their來指代性別不明的單個人（即單數）。如：

Everyone knows what they have to do, don’t they? 每個人都知道自己必須做什么，對嗎？

If either David or Janet come, they will want a drink. 大衛或珍妮特來的話，是會要喝酒的。

If any of them comes to see me, let them wait for me to come back. 如果他們中有人來看我，請叫他們等我回來。

When a person gets married, they have to start thinking about their responsibilities. 一個人結了婚，他們就得考慮考慮自己的責任。