What is a primary ingredient in McDonald's Chicken McNuggets?

The primary ingredient in McDonald's Chicken McNuggets is chicken breast. This choice is correct because Chicken McNuggets are specifically made from meat derived from chicken, primarily comprising chicken breast meat that is ground and mixed with a blend of seasonings and other ingredients to create the nugget's texture and flavor.

Other options like turkey, beef, and fish represent different types of protein that are not used in the formulation of Chicken McNuggets. McDonald's has built its product identity around chicken for this particular item, which focuses on providing a specific taste and texture profile representative of chicken nuggets. Therefore, the selection of chicken breast as the primary ingredient underlines the product's branding and consumer expectations.