The correct answer is option 4: the death of songbirds due to eating insects poisoned with pesticides. In her book, Silent Spring, Rachel Carson documents the harmful effects of chemical pesticides, particularly DDT, on the environment. She focused on how these pesticides were affecting the bird population, specifically songbirds. Carson observed that the widespread use of pesticides was resulting in the decline of birds due to the ingestion of insects that were contaminated with these chemicals. The title of the book, Silent Spring, symbolizes the absence of the chirping and singing of birds in an environment that has been poisoned by pesticides. Carson`s book brought attention to the detrimental impact of pesticides on wildlife and played a significant role in raising awareness about the need for environmental conservation and the dangers of chemical pollution.