The correct preposition is "to" because we are making a comparison between two things.
The phrase "compared to" is used to show similarity or equivalence between two items.
"And" (1) does not fit in this context because we are not connecting two items but making a comparison.
"By" (3) refers to the agent performing an action and doesn’t work in this context.
"At" (4) is used for indicating location, not for comparisons. Conclusion:
"To" is the correct preposition to use when making a comparison between two items.