Which of the following was not an early (pre-1900) pesticide?

DDT, or dichlorodiphenyltrichloroethane, is the correct answer because it was developed in the 1940s, long after the pre-1900 era. DDT became popular during World War II for its effectiveness in controlling insects and was widely used thereafter until it was banned in many countries due to environmental and health concerns.

On the other hand, Bordeaux Mixture, nicotine, and sulfur were all utilized as pesticides prior to 1900. The Bordeaux Mixture, which consists of copper sulfate and lime, has been used since the 1880s for controlling fungal diseases in plants. Nicotine was used as a natural insecticide in the 19th century. Sulfur has a long history of use as a fungicide and insecticide, dating back to ancient times. Therefore, DDT stands out as the only option that emerged in a much later timeframe, making it the one that was not an early pesticide.