The Sun shines by _______ reactions.

• A. chemical combustion
• B. photosynthetic
• C. nuclear fission
• D. nuclear fusion

Answer: (D)

Verified step by step guidance

1. Understand the question: The problem is asking about the type of reaction that powers the Sun and provides its energy.
2. Recall the concept: The Sun generates energy through nuclear reactions occurring in its core. Specifically, it involves the fusion of hydrogen nuclei into helium.
3. Differentiate the options: Chemical combustion involves the reaction of substances with oxygen to release energy, which is not sufficient to power the Sun. Photosynthesis is a biological process in plants, not applicable to the Sun. Nuclear fission involves splitting heavy atomic nuclei, which is not the process occurring in the Sun.
4. Focus on nuclear fusion: In the Sun, nuclear fusion occurs when hydrogen nuclei (protons) combine under extreme pressure and temperature to form helium, releasing a tremendous amount of energy in the process.
5. Conclude: The correct answer is nuclear fusion, as it is the process responsible for the Sun's energy production.