Energy from the sun comes from fusion. What happens during that reaction?

• A. Two hydrogen nuclei combine to form a helium nucleus, releasing energy.
• B. Oxygen atoms combine to form water molecules, releasing energy.
• C. Helium nuclei split into hydrogen nuclei, absorbing energy.
• D. Carbon atoms fuse to form nitrogen, releasing energy.

Answer: (A)

Verified step by step guidance

1. Understand that nuclear fusion is a process where lighter atomic nuclei combine to form a heavier nucleus, releasing energy in the process.
2. Identify the most common fusion reaction in the sun, which involves hydrogen nuclei (protons) combining to form helium nuclei.
3. Recognize that during this fusion, the mass of the resulting helium nucleus is slightly less than the total mass of the original hydrogen nuclei, and this mass difference is released as energy according to Einstein's equation \(E = m c^{2}\).
4. Note that other options like oxygen atoms combining to form water or helium nuclei splitting into hydrogen are not fusion reactions relevant to the sun's energy production.
5. Conclude that the correct description of the sun's fusion process is two hydrogen nuclei combining to form a helium nucleus, releasing energy.