Which of these is not an official grade of apples?

The official grades of apples are established to ensure quality and consistency in the market. The grading system provides clear classifications that reflect the quality, size, and condition of the apples.

"US Extra Fancy" and "US Fancy" refer to high-quality grades of apples. The "US Extra Fancy" grade is the top tier, indicating the best quality, while "US Fancy" is slightly lower but still signifies high standards. "US Standard" also exists in the grading system, representing a quality level that meets basic criteria.

In contrast, "US Commercial" is not an official grade within the established USDA grading standards for apples. The term is often used in various contexts but does not correspond to an official grading category. This distinction makes it clear why this option is correct, as it does not align with the formal classifications used to grade apples.