If the major difference between a brownie recipe and a muffin recipe is buttermilk and baking soda, what must these two do to the muffin mixture?

A) Prevent it from rising.
B) Make it dense.
C) Make it lighter and airier.
D) Cause it to be chewier.

Buttermilk

Traditionally, the liquid left after churning butter from cream; now often commercially produced by adding lactic acid bacteria to milk.

Baking Soda

A white crystalline compound (sodium bicarbonate) used in baking as a leavening agent due to its ability to release carbon dioxide when heated or mixed with acidic substances.

Muffin Mixture

A batter specifically prepared for making muffins, usually containing flour, eggs, a leavener, liquids like milk or water, and other flavoring agents.