Which of the following characteristics might typically define an adjuvant?

An adjuvant is defined as a substance that is added to a pesticide formulation to enhance its performance. This can include improving the effectiveness of the active ingredient, increasing the spread and adhesion of the pesticide on the target surface, or modifying the physical properties of the mixture for better application. Therefore, the characteristic that an adjuvant "has chemicals to enhance pesticide performance" accurately captures the essential role of adjuvants in pesticide applications, differentiating them from the active ingredients themselves.

The other characteristics do not accurately describe the role of adjuvants. While some adjuvants may act as carriers, they serve a broader role that includes enhancing efficacy beyond mere delivery. Not all adjuvants are synthetic; many natural adjuvants exist as well. Lastly, while it may be possible to conduct some pesticide applications without adjuvants, they are often recommended or required to maximize effectiveness and ensure better control of pests, which makes the assertion that they are "not necessary in most applications" misleading.