Which of the following is a major source of sodium in the average diet?

Processed and packaged foods are a major source of sodium in the average diet because they often contain added salt for flavor enhancement, preservation, and as a stabilizer. These foods, including snacks, canned goods, frozen meals, and fast food, tend to have significantly higher sodium levels compared to whole or fresh foods.

In contrast, fresh fruits and vegetables, while nutritious, are naturally low in sodium. Whole grains contain some sodium but are not nearly as significant a source as processed options. Nuts and seeds also contain sodium, particularly if they are salted, but they typically contribute less sodium to the average diet relative to processed and packaged foods. Therefore, it is clear that processed and packaged foods are the leading contributors to sodium intake, making them the correct choice.