What is the primary purpose of a selective herbicide?

The primary purpose of a selective herbicide is to control certain types of plants, particularly weeds, while leaving other desirable plants unharmed. This targeted approach allows farmers and gardeners to manage unwanted vegetation without damaging the crops or plants they wish to protect. Selective herbicides work by targeting specific physiological processes or characteristics unique to particular plant species, which minimizes collateral damage to surrounding flora.

In contrast, options that suggest controlling all types of plants imply a non-selective herbicide that indiscriminately kills any plant it contacts, which is not the function of a selective herbicide. The option about eliminating pests from the soil pertains to pesticides that target insects or other pests, rather than herbicides, which focus on plant life. Lastly, enhancing the growth of crops does not relate to herbicides; instead, this function is typically associated with fertilizers or growth stimulants, not herbicide use. Thus, the second option accurately reflects the intended use of selective herbicides.