What is the definition of a "Pesticide"?

The definition of a "Pesticide" encompasses a broad range of substances that are utilized to manage, control, or eliminate pests. This includes not only chemicals but also substances derived from natural sources. By defining a pesticide as any substance used to kill or manage pests, the correct answer reflects the comprehensive nature of pest control products. This definition recognizes that pesticides can be synthetic or natural, and may include herbicides, insecticides, fungicides, and other agents that affect various types of pests, including insects, weeds, fungi, and other unwanted organisms.

The other options are too restrictive. The first option limits pesticides solely to substances that kill pests, excluding those used for management and control. The third option inaccurately confines pesticides to only synthetic chemicals, and the fourth option suggests that the only valid pest control methods are those that are natural, neglecting a significant segment of available pesticides, especially those that are synthetic. This thorough understanding of what constitutes a pesticide is key for anyone working with or studying pest management regulations and practices.