If the highest elevation is sea level, it must be a body of water, probably a large sea. 17.6 milliom km[sup]2[/sup] is about twice the size of Australia.
You sure about that number in 1) ? That’s about 1/10 the size of the Pacific Ocean. Too big to be any country except Russia, and the other clues point away from that. If you got the decimal point wrong, at 176m sq km it is the Pacific Ocean.
I suppose it could be some construct such as Micronesia, but I don’t belive that’s big enough to qualify.
Number 1 is correct, though she has it as larger than the U.S. I was thinking something like the Indian Ocean or along those lines. With the high elev being sea level it has to be something involving a body of water.