DDT was widely used as a pesticide for 20 years. Its use was banned after studies showed severe side effects were evident in humans, the environment, and animals as a result of DDT. Why were the side effects of DDT so harmful?
A. DDT kills insects and other pests.
B. DDT decomposes.
C. DDT was genetically engineered.
D. DDT bioaccumulates.

Bioaccumulation is the accumulation of substances or compounds such as pesticides, fertilizers or other chemicals in the body of the organisms. These substances or compounds are toxic and remain undigested in the body of the organisms are transferred subsequently in a food chain, when one organism is consumed by another organism. The highest trophic level is most effected because of the concentration of the toxic substance is the maximum.

DDT (dichlorodiphenyltrichloroethane) is a colorless, odorless and tasteless crystalline chemical compound. It is used as a pesticide to kill pests in agricultural field. DDT is highly toxic chemical compound. It remains undigested in the body of the organism and transferred in a food chain when one organism is consumed by another organism. The effect of DDT is magnified several times in the top most trophic level in the food chain due to bioaccumulation.