Which of the following is defined as a chemical that can kill certain types of plants?

Herbicides are specifically designed to target and kill certain types of plants. They are used in agriculture, landscaping, and forestry to control unwanted vegetation, such as weeds, that compete with desired crops or plants for resources.

The classification of herbicides can range based on their selectivity; some are non-selective and kill all plant life they come into contact with, while others are selective, designed to target specific plant species without harming others nearby. This focus on plants distinguishes herbicides from the other chemical agents listed.

Pesticides is a broader category that encompasses any chemical used to kill pests, which includes herbicides but is not limited to them. Insecticides target insects specifically, while fungicides are meant to combat fungal infections. Thus, while herbicides fall under the pesticide umbrella, it is their specific action on plant life that precisely defines them as the correct answer in this context.