Which of the following best describes selective herbicides?

Selective herbicides are specifically formulated to target particular weed species while leaving desirable plants relatively unharmed. This characteristic allows for the effective control of unwanted vegetation in agricultural and landscape settings without damaging the crops or plants that are meant to thrive. The ability to selectively eliminate certain weeds makes these herbicides especially valuable in integrated pest management practices.

In contrast, the other options do not accurately describe selective herbicides. The first option, which states that they kill all vegetation, refers to non-selective herbicides, which indiscriminately kill any plant they come into contact with. The third option regarding non-toxicity to mammals is also misleading; while many selective herbicides may pose low risks to mammals when used according to guidelines, this isn't universally true for all products. Lastly, the fourth option suggests that selective herbicides are ineffective in wet conditions, which is not inherently true for all selective products, as their effectiveness can vary based on formulation and environmental conditions. Thus, option B is the best choice, accurately capturing the defining feature of selective herbicides.