There are many different Aboriginal languages, however most aboriginals speak English as well and many of them only speak English
Yes, both countries speak English as their main language.
They all spoke the same language
They don't actually speak different languages; they just speak different variations of the same language. The variations differ depending on where they are from, just like in China you can speak Mandarin or Cantonese depending on which part of China you came from.
English is the main language spoken in Australia, spoken by around 78.5% of the population. Australia has no official language and no declared national language. English is the default language throughout the country.
It means that you speak in the same language
The same language I speak in any location.
They speak English
You speak the same language you spoke at the beginning of World War I.
Australia does not have an official language.English is the default language throughout Australia, so "thank you" remains the same.
For the same reason you speak English. That's their language. (However English is not your native language, I think)
Australia has never had an official language, then or now. However, in the 1800s, the most commonly spoken language in Australia was the same as it is now - English.
Each person would speak the same language. Same can be said about any language.