their的形容词性物主代词和名词性物主代词

例句：

I joined my wail to theirs, loud and bitter.

我和他们一起恸哭，哭声又高又痛苦。

Japan's higher education is superior to theirs.

日本的`高等教育比他们的好。

Both England and the US said the island was theirs.

英国和美国都说这个岛是他们的。