India is a key participant in the International Thermonuclear Experimental Reactor (ITER), a global nuclear fusion research and engineering megaproject. ITER is set to become the world's largest magnetic confinement plasma physics experiment, aiming to demonstrate the feasibility of fusion as a large-scale, sustainable energy source.

India's involvement in ITER provides technological expertise, research collaboration, and industrial capabilities, which can significantly contribute to its future efforts in developing nuclear fusion reactors for commercial power generation. By participating in this international project, India gains access to cutting-edge advancements in fusion technology, potentially paving the way for its own fusion-based energy infrastructure. Hence, the correct answer is option D.