What does selectivity of a herbicide refer to?

Selectivity of a herbicide refers specifically to its ability to cause injury to certain types of plants while leaving others unharmed. This characteristic is crucial in the context of controlling unwanted vegetation, as it allows for the targeted eradication of specific weeds or invasive plant species without damaging desirable plants in the vicinity.

Selective herbicides are designed to exploit physiological differences between plant species, which means they can effectively disrupt growth processes in certain plants while being safe for others. This selectivity is essential for integrated pest management practices, helping to maintain biodiversity and protect crops or ornamental plants.

The other options do not accurately capture the concept of selectivity. For instance, the ability to kill all types of plants does not align with the definition of selectivity, which inherently involves differentiation among plant responses. Furthermore, effectiveness in any type of soil pertains to the herbicide's performance rather than its selectivity, and the impact on animal life is unrelated to the selective action of herbicides on plants.