Answer: B) Outside is to inside.
Explanation: an analogy is a comparison between two things, usually to help clarify or explain something. In the given prompt we have the words downside and upside, we can see that they are antonymes (so we can directly discard option A, because big and large are synonyms), and also they are referring to opposite sides of something, so from the given options, the option that have the same relationship as "downside is to upside" is "outside is to inside."
