What type of herbicide is designed to break down quickly in the environment?

The chosen answer is correct because a non-residual herbicide is specifically formulated to break down quickly in the environment, thereby minimizing its long-term impact on surrounding ecosystems. This type of herbicide works by rapidly degrading once it has served its purpose of controlling unwanted vegetation, which reduces the likelihood of persistence in the soil or water systems.

In contrast, selective herbicides target specific plant species without harming others, but they may not necessarily degrade quickly. Non-systemic herbicides refer to those that do not move within the plant system after application, while contact herbicides kill only the parts of the plant they contact, without necessarily breaking down rapidly in the environment. Thus, while all these terms pertain to different aspects of herbicides, only non-residual specifically highlights the quick environmental breakdown characteristic that makes it the correct choice in this context.