In stellar fusion, hydrogen fusion leads to the formation of which sequence of elements up to iron?

• A. Elements up to iron
• B. Only helium
• C. Elements up to carbon
• D. Elements beyond iron

Answer: (A)

The key idea is that stars build heavier elements through successive fusion stages, starting from hydrogen. Hydrogen fusion converts hydrogen into helium, releasing energy to power the star. As the star evolves, helium burning creates carbon and oxygen, and those products fuse to form progressively heavier elements—neon, magnesium, silicon, sulfur, and so on—in massive stars all the way up to iron. Iron marks the practical end of energy-producing fusion in stars, so the overall sequence produced by stellar fusion extends up to iron. That’s why the best answer is that elements formed through this process span elements up to iron. The other options miss either the later burning stages beyond helium, or imply fusion beyond iron, which isn’t how stellar fusion proceeds to release energy.