Which herbicide kills or controls almost all plants and weeds, including desirable plants?

The correct choice is a nonselective herbicide, as this type is designed to target and kill a wide range of plants, including both weeds and desirable vegetation. Nonselective herbicides work by disrupting the physiological processes common to many plants, leading to their death. This broad-spectrum action makes them effective for clearing out plants in areas where no specific species is desired, such as during land clearing or in non-crop areas.

Understanding the specific nature of nonselective herbicides is crucial for effective application. Since they can harm all plants in the treated area, careful application is essential to avoid damage to desirable plants. This characteristic differentiates them from selective herbicides, which target specific weed species while leaving desirable plants unharmed.

Other types of herbicides, such as residual and systemic herbicides, serve different purposes. Residual herbicides remain active in the soil and prevent germination of weeds for an extended period, while systemic herbicides are absorbed by plants and disrupt their internal processes, but may not impact all plant species. Therefore, nonselective herbicides are uniquely effective at controlling almost all plants and weeds in a given area, which is what makes them the correct answer.