The energy reaching Earth from the Sun is produced by which reaction?

The correct answer is Fusion Reaction. The Sun's energy is produced by nuclear fusion, specifically the fusion of hydrogen nuclei (protons) into helium nuclei in the Sun's core. This process releases immense amounts of energy in the form of light and heat. Among the options:

• Fission Reaction: Used in nuclear reactors and atomic bombs, not in stars like the Sun.
• Combustion Reaction: A chemical reaction involving burning, not the Sun's energy source.
• Chemical Reaction: Produces relatively small amounts of energy, not the vast amounts emitted by the Sun.
• Fusion Reaction: Correct; the Sun is powered by nuclear fusion.

Therefore, the correct answer is "Fusion Reaction".