What condition exempts a drug from being classified as adulterated according to standards?

A drug can be exempted from being classified as adulterated if the differences in quality are clearly stated on its label. This means that if a drug's label provides transparent information about its composition and any variations in quality, consumers and health professionals are made aware of what they are using. This labeling allows for informed choices, ensuring that users understand any potential differences that could affect the drug's efficacy, safety, or functionality.

This provision helps to maintain standards of transparency and accountability within the pharmaceutical industry, as it combats the risks associated with hidden variances in drug quality. By indicating variations, manufacturers can avoid misleading consumers and eliminate potential misunderstandings regarding the drug's characteristics.

The other options do not directly relate to the criteria for exemption from adulteration based on quality differences being disclosed. Therefore, the focus is on the importance of labeling as a means to manage expectations and provide clarity on the product's qualities.