The correct answer is option 4, chlorophyll. Chlorophyll is the pigment involved in photosynthetic activity. It is the main pigment found in the chloroplasts of plants, algae, and some bacteria. Chlorophyll absorbs light energy from the sun and converts it into chemical energy through the process of photosynthesis. This pigment is responsible for the green color of plants. Option 1, anthocyanin, is a pigment responsible for red, purple, and blue colors in plants and fruits but is not involved in photosynthesis. Option 2, fucxanthin, is a pigment found in brown algae and is not directly involved in photosynthesis. Option 3, carotenoid, is a group of pigments that includes colors ranging from yellow to orange and is also involved in photosynthesis, but chlorophyll is the primary pigment involved in this process.