Question

South Asia is actually a ____________, a large landmass within a continent

Answer 1

I don't know whether this was one of your options, but South Asia can be very well characterized as  a Sub-continent.

In fact, it's is commonly referred to as "the Indian Subcontinent" or even simply "Subcontinent". One of the reason for a distinction of this part of the land is that it lies on a different tectonic plate.
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