What is 'a sing-along medley'?
In the sentence below:

Australia – the sixth-largest country on this lonely planet – is dazzlingly diverse: a sing-along medley of mountains, deserts, reefs, forests, beaches and multicultural melting-pot cities.

What does ' a sing-along medley' mean?

Question

What is 'a sing-along medley'?
In the sentence below:

Australia – the sixth-largest country on this lonely planet – is dazzlingly diverse: a sing-along medley of mountains, deserts, reefs, forests, beaches and multicultural melting-pot cities.

What does ' a sing-along medley' mean?

Answer

It's a poetic way to say that all its landscapes - mountains, deserts, etc. - work together just like songs fitted together. The 'sing-along' part means that you get drawn into it, involved with it. 
I hope that helped, I'm not the best at explaining things! :)

Answer

Please forgive me wiriting in Chinese.

澳大利亚是世界上国土面积第六大的国家，孤独地呆在这个星球上(Hope I didn't change its meaning.)，但其实它却是个相当多样化的国家，有高山、沙漠、珊瑚(沙洲 I don't know which is the best word.)、森林、海滩，还有文化大熔炉的城市，就像一部欢快的歌曲大串烧。

感觉像是一本相当有水平的旅游杂志。

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