Which of the following describes the term 'adjuvants'?

The term 'adjuvants' refers to substances that are added to a pesticide formulation to enhance or modify the performance of the primary pesticide active ingredient. Specifically, adjuvants can serve various purposes, such as improving the application process, enhancing the efficacy of the pesticide, increasing spreading and sticking capabilities, or helping with the formulation's stability.

By being inert substances, adjuvants do not contribute to the pesticidal action themselves but instead assist in optimizing the effectiveness of the pesticide they accompany. This can include surfactants, oils, and other substances that help improve coverage or penetration of the pesticide into the targeted pest or plant.

The other options do not accurately describe adjuvants. For example, additives that enhance herbicide efficiency indeed capture part of their function, but it is not a comprehensive description and focuses narrowly on herbicides specifically. Ingredients that increase toxicity or components that make pesticides less effective are mischaracterizations, as adjuvants do not solely aim to increase toxicity nor do they work to diminish the effectiveness of pesticides.