Final answer:
Salad dressing and air are both best classified as heterogeneous mixtures. Saltwater, soda, vinegar, and milk are examples of homogeneous mixtures.
Step-by-step explanation:
The correct answer is A) Salad dressing, air. Salad dressing is a heterogeneous mixture because it is made up of multiple components that are not uniformly distributed. For example, oil and vinegar do not mix thoroughly in salad dressing, resulting in clearly visible separate layers. Air is also a heterogeneous mixture because it is composed of various gases, such as nitrogen, oxygen, carbon dioxide, and others. These gases are not evenly distributed throughout the atmosphere.
In contrast, saltwater and soda are both examples of homogeneous mixtures. In saltwater, sodium chloride (salt) is dissolved uniformly in water, creating a single phase. Similarly, soda is a homogeneous mixture of carbon dioxide, sugar, flavorings, and water, where these components are evenly distributed.