The correct answer is option 4, Caventou and Pelletier. Chlorophyll, the green pigment responsible for photosynthesis in plants, was first isolated and named by two French chemists named Joseph-Bienaimé Caventou and Pierre Joseph Pelletier. They were able to extract and identify the pigment from plants through a series of experiments in the early 19th century. It is important to note that options 1, 2, and 3 are all related to the discovery and study of chlorophyll, but the specific credit for isolating and naming the pigment goes to Caventou and Pelletier.