Which layer of the sun is responsible for producing all of the sun's energy through nuclear reactions?

• A. Core
• B. Radiative Zone
• C. Convective Zone
• D. Photosphere

Answer: (A)

The main concept tested is where nuclear fusion occurs to power the Sun. In the core, extreme temperatures and pressures allow hydrogen nuclei to fuse, mainly through the proton–proton chain, forming helium and releasing energy. This energy is generated there and then travels outward through the radiative zone and the convective zone before reaching the surface. The radiative zone moves energy outward by photon diffusion, the convective zone carries energy through circulating plasma, and the photosphere is the visible surface from which light escapes. Since fusion happens in the core, that layer is responsible for producing all of the Sun's energy.