What is the primary energy source powering the Sun through fusion in its core?

• A. Nuclear Fusion
• B. Solar Wind
• C. Gravitational Contraction
• D. Chemical Combustion

Answer: (A)

Energy in the Sun’s core comes from nuclear fusion, where hydrogen nuclei fuse to form helium. In this process a small amount of mass is converted into a large amount of energy, released as photons and neutrinos, which steadily heat and light the Sun. The core temperatures and densities are so extreme that protons can collide and fuse via the proton–proton chain, sustaining the Sun’s energy output for billions of years.

Other options don’t fit: solar wind is a stream of particles emitted from the Sun, not the source of its internal energy. Gravitational contraction powered the Sun in its early formation but is no longer the main energy source today. Chemical combustion cannot occur in the Sun’s hot, ionized plasma, and even if it could, it would yield far less energy than fusion.