Which of the following is a major part of a tree responsible for photosynthesis?

The major part of a tree responsible for photosynthesis is the leaves. Leaves contain chlorophyll, the green pigment that absorbs sunlight, which is crucial for the photosynthesis process. During this process, plants convert sunlight into chemical energy, using carbon dioxide from the air and water from the soil to produce glucose and oxygen.

While roots, trunks/stems, and flowers play essential roles in a tree's overall health and reproduction, they do not directly engage in the photosynthesis process. Roots primarily absorb water and nutrients from the soil, trunks and stems provide structural support and transport substances throughout the tree, and flowers are involved in reproduction but do not contribute to photosynthesis. Therefore, leaves are uniquely adapted for capturing sunlight and facilitating the production of energy through photosynthesis, making them the correct answer to the question.