Final answer:
Joey made a 'mixture' for breakfast by combining milk and cereal, which is a convenient and nutritious breakfast option.
Step-by-step explanation:
When Joey pours a glass of milk over a bowl of dry cereal, the combination of these two elements can be best described as a 'mixture'. A mixture is a combination of two or more substances that are not chemically combined. In this case, the milk and cereal retain their properties which are seperate from each other and can be physically separated. In the context of breakfast, this combination is chosen for being quick to prepare, nutritious, and customizable to personal tastes.