Which name category refers to the active ingredient that remains the same among different producers?

The correct choice is the common name. The common name refers to the active ingredient in a pesticide that is universally recognized and remains consistent across different manufacturers. This standardized term allows users, such as applicators and researchers, to easily identify and communicate about the active ingredient regardless of the brand or trade names used by different companies.

For example, the active ingredient glyphosate is known by the common name "glyphosate," despite being marketed under various trade or brand names by different companies. This nomenclature is crucial in ensuring clarity in the industry, enabling better understanding of safety, efficacy, and environmental impact of the chemical across various contexts.

The other names listed serve different purposes: the trade name refers to the specific name given by a manufacturer to a product, which can vary; the chemical name refers to the precise chemical structure, which is typically more complex and technical; and the brand name is essentially a version of the trade name that is often seen in marketing. None of these maintain the same identification across producers in the way the common name does.