Let's take water: it definitely has three forms: ice, liquid and water vapor: it's definitely the correct answer!
Wind is just movement of air, so it can't be in any other state.
And as far as air and soil are concerned: some parts of them can also appear in three states, but not the air or soil generally, for example water is included in both of them and it can appear in the three states!
The answer you are looking for is B
Coastal Plains has the most geographic subsection
The country Mongolia was like a buffer state between Russia and China. By definition, a buffer state is a country that's in between two countries or any powerful countries. Both countries sometimes come into agreement of occupying a certain part of the buffer state and can also cause war.
