Herbicides are primarily used for what purpose?

Herbicides are specifically designed to control and eliminate unwanted plants, commonly referred to as weeds. These chemicals function by targeting certain physiological processes unique to plants, allowing for the selective killing of pest plants while often leaving desirable crops unharmed. This is critical in agriculture, as effective weed management is essential for maximizing crop yield and ensuring that crops have access to necessary nutrients, water, and sunlight that would otherwise be competed for by weeds.

The other options, such as promoting crop growth, fertilizing soil, or enhancing water retention, do not align with the primary function of herbicides. While promoting growth and improving soil conditions are important aspects of agriculture, those objectives would typically involve the use of fertilizers, soil amendments, or other cultural practices rather than herbicides. Therefore, the use of herbicides is correctly identified as a means to manage weed populations effectively.