What does the word "rarefy" mean?

The word "rarefy" means to make something thinner, sparser, or less dense. This term is often used in contexts relating to the reduction of mass or density in a substance, such as air or a liquid. In a broader sense, it can also refer to making concepts or ideas more abstract or refined. The correct choice reflects the primary meaning associated with "rarefy," which emphasizes the idea of thinning or diluting something. The other answer choices suggest actions like strengthening or enhancing quality, which do not align with the established definition of "rarefy."