Which best describes the actions included in "rubbing in"?

The term "rubbing in" specifically refers to a technique primarily used in baking where cold fat, such as butter, is incorporated into flour. This is achieved by using fingers or a pastry cutter to rub the fat into the flour until the mixture resembles coarse crumbs or a breadcrumb-like texture. This process helps to create a light and flaky texture in baked goods like scones or pastry, as it allows air to be trapped in the mixture.

The other choices describe different culinary techniques that do not match the specific process of rubbing in. For instance, mixing liquid with dry ingredients refers to a general combining method in baking but does not involve integrating fat into flour as rubbing in does. Heating ingredients to meld flavors pertains to a cooking technique focused on enhancing taste through heat, while layering dough for pastries deals with creating flaky layers, which is distinct from the rubbing in method. Thus, the most accurate description of rubbing in is indeed combining butter with flour to create a crumb-like texture.