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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Its a strait (B) All the other answers aren't logical
C. Nuclear to be honest, I don’t know, but I think this is the answer.
Hey,
The Chao Phraya River is considered an artery because it is used to transport people and goods.
Hope it helps u