I believe its the last one: 95% of the surface of Antarctica, which contains 70% of Earths freshwater supply, is covered by ice.
It does not really matter which form you write in. However, writing in the third person omniscient is generally more effective for essays. If you were writing, say, a blog, you would use the first person, but in this case, I think you want to use the third person.
Is this the whole question??
