How many continents are there on Earth?

There is no geological law that fixes the number of continents, which is why the answer depends on where you went to school. The seven-continent scheme splits the landmasses into Asia, Africa, North America, South America, Antarctica, Europe and Australia, and it is the version used in Britain, the United States, India, China and most of the English-speaking world. It is a cultural rather than a physical division, most obviously between Europe and Asia: the two sit on a single continuous landmass and are separated only by the conventional line of the Urals, the Ural River, the Caspian Sea and the Caucasus. Elsewhere teachers combine those two into Eurasia, or merge the Americas into one, producing six- or five-continent models that are equally defensible. When a quiz asks the question without qualification, seven is the expected answer, because that is the scheme printed in the atlases the question was written from.

Antarctica has no permanent population at all, only rotating crews at research stations.