Which of Earth's resources can be transformed into a solid, a liquid, or a gas?

a. air

b. water

c. soil

d. wind

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!