Final answer:
Refrigerator and freezer cabinets are typically constructed using sheet metal, although some may use plastics or stainless steel in high-end models.
Step-by-step explanation:
The exterior shells of most refrigerator and freezer cabinets are typically formed from sheet metal, specifically, option D) Sheet metal. However, there are some models that use plastics or a combination of both metals and plastics for the exterior surfaces. In high-end or commercial models, stainless steel can be used for its durability and aesthetic appeal. Aluminum, being a lightweight and conductive material, is less commonly used for the exterior, but it may be found in internal components or in certain specialty refrigeration units where weight is a concern.