The correct answer is: A. in
The preposition “in” is used to indicate a location within a place. In this case, the speaker is saying that the person lives in Australia.
The preposition “at” is used to indicate a specific location, such as a house or a street address. In this case, the speaker is not saying that the person lives at a specific location in Australia, but rather that they live in Australia in general.
The preposition “for” is used to indicate a period of time. In this case, the speaker is not saying that the person lives in Australia for a specific period of time, but rather that they live there permanently.
The preposition “none of the above” is used to indicate that none of the other options are correct. In this case, the preposition “in” is the correct answer.