Answer;Four hydrogen nuclei join to form a helium nucleus, two neutrinos, and energy.Explanation;Nuclear fusion is the process of nuclear reaction in which two light atomic nuclei combine to form one heavier atomic nucleus. Nuclear fusion reactions occurs naturally, for example in the stars and the sun. Hydrogen gas in the sun is normally used up in nuclear fusion reactions to yield helium gas. Hydrogen nuclei in the core of the sun fuse with each other to form helium atoms nuclei together with energy.That is; 4 hydrogen nuclei → fuse → 1 helium nucleus + energy