Which answer represents a central idea from descartes?
all humans are born with a blank slate.
i think, therefore i am.
our world is the best possible world god could have created.
the material world is not real; we are only thoughts existing inside the mind of god.

The answer that represents a central idea from Descartes is - I think, therefore I am.
This means that as long as you are able to convey thoughts, you truly exist. So if you doubt your existence, you are still thinking about it, which means that you do exist.
The first thought was formed by John Locke, the third by Gottfried Leibniz, and the final one by George Berkeley.