What is the alphanumeric name of the most popular of three audio encoding layers in an MPEG standard released in 1993?

Alphabetically, which of Snow White's seven dwarfs comes first? Listed alphabetically by last name, which U.S. vice president comes first? Alphabetically, which noble gas comes last? Alphabetically, which planet in our solar system comes last? Which author, already a successful poet, began his career as a novelist in 1814 with a tale of the Highlands? Which German-born biochemist discovered the citric acid cycle of metabolism and energy production? Al Gore's 1992 book on the environment was titled "___ in the Balance"? Alsace-Lorraine was annexed by Germany as a result of which 1870-71 war?