Contact herbicides are used to:

Contact herbicides are designed to act on the parts of the plant that come into direct contact with the chemical. When applied, they destroy or injure the exposed plant tissues, primarily affecting the leaves and stems. This means that only the areas that the herbicide touches will experience its effects, leading to the plant's decline or death.

This focused action differentiates contact herbicides from systemic herbicides, which are absorbed by a plant and move through its system to affect the entire plant, including roots that may not be directly contacted by the herbicide. Contact herbicides do not prevent all types of plant growth, as they do not inhibit growth at the root level or affect plants that are not directly contacted. Therefore, option B accurately describes the mechanism and limitation of contact herbicides.