As Australia is considered a continental landmass, it is almost always defined as not being an island. I wasted way too much time trying to figure out this answer.
I think the implication is borders with different countries. That said, I would still call Canada a one-border country, regardless of Hans Island. It's essentially a rock... tiny, isolated, uninhabited, and unknown to most.
Greenland is the largest island in the world, sovereign or not. Australia is the smallest continent by common convention throughout the world, but it is not a scientific rule; thus I can say the Americas is made up of primarily one very large island or that Afro-Eurasia is the largest island on the planet. The test should align with common convention.
Madagascar is the largest island country made up of mostly one island. However, Indonesia is the largest island country.
I think in the context of this quiz it's fine to make Australia the answer to this question, as it's the largest landmass belonging to just one country (in the sense that Afro-Eurasia would be the largest island country if it were all one country).
Silliness. Ignore these people who want to count podunk who cares island as a real border between Denmark and Canada. If you start adding random territory borders then we’ll have to start adding Antarctica borders before too long.
Madagascar is the largest island country made up of mostly one island. However, Indonesia is the largest island country.
Australia is a landmass not an island, the biggest island country is Madagascar
Canada borders US and Denmark, so two borders
Biggest one border country: Papua New Guinea.
Biggest two border country: Canada.
Please update!