The correct answer is option 4, insects. Pesticides are chemicals that are used to eliminate or control pests, which typically include insects such as mosquitoes, flies, cockroaches, termites, and agricultural pests that can damage crops. Pesticides are specifically designed to target and eliminate these insects, usually by disrupting their nervous system or reproductive processes. They are commonly used in agriculture and gardening to protect crops and plants from pests that can reduce yield and cause damage. While pesticides can also be used to control other pests such as rodents or weeds, the primary purpose is to target and destroy insects.