Which LD number indicates the highest toxicity in pesticides?

The LD50 number refers to the lethal dose of a substance that causes death in 50% of a test population, typically laboratory animals like rats or mice. The lower the LD50 value, the higher the toxicity of the substance, as it takes a smaller dose to be lethal.

In this case, an LD50 number of 51 indicates that a higher dose is required to reach lethal levels compared to an LD50 of 10. This means that substances with a lower LD50 are more toxic. Therefore, among the choices, the LD50 number that indicates the highest toxicity is indeed the one with the lowest value, which here is 10. It is important to understand the context of these numbers; they serve as a critical measure in evaluating and comparing the safety and toxicity of various pesticides.