What forms the effervescent tablet?

Effervescent tablets are specifically designed to dissolve in water, releasing carbon dioxide gas as a result of a chemical reaction between an acid and a carbonate or bicarbonate. This reaction produces effervescence, which is the bubbling and fizzing effect you see when the tablet is added to water. The release of gas helps to dissolve the tablet quickly, making it easier to ingest and often providing a refreshing taste.

While the other options mention various forms of medication delivery, they do not accurately describe the composition and mechanism that characterize effervescent tablets. Antacids combined with active medication represent a different formulation, the gelatin shell refers to a capsule form, and oral disintegrating tablets use a different process for dissolution. Thus, the option highlighting the acid and carbonate or bicarbonate clearly defines the unique chemical reaction that makes effervescent tablets distinct.