Meat graded "US Standard" is the grade given at the:

The grading of meat, including the designation "US Standard," is primarily determined at the time of slaughter. During this phase, the quality of the animal is assessed based on various factors such as age, fat composition, and muscle development. The USDA inspects the meat and assigns the grade, which informs consumers and retailers about the expected quality and characteristics of the meat. Meat graded "US Standard" indicates a lower quality than higher grades (such as Prime or Choice), but it is still deemed acceptable for sale. This grading is critical for setting market expectations and ensuring that meat products meet certain standards before reaching consumers.

While the other options relate to different points in the meat distribution process, they do not determine the grade itself. For instance, the time of purchase or delivery relates more to market dynamics and availability rather than the inherent grading of the meat.