Nuclear fusion powers the Sun

Steps:

• Recognize that fusion of hydrogen to helium occurs in stellar cores via the proton-proton chain.
• Recall this process releases energy from mass defect converted to energy (E=mc²).
• Eliminate options involving decay or non-stellar processes.
• Confirm the Sun's core as the site of hydrogen-helium fusion.

Why D is correct:

• In the Sun's core, high temperature and pressure enable hydrogen nuclei to fuse into helium, releasing energy per Einstein's E=mc² from the mass difference.

Why the others are wrong:

• A: Carbon-14 decay is beta emission, a fission-like process, not fusion.
• B: Alpha particle emission is radioactive decay releasing a helium nucleus, not forming it via fusion.
• C: Earth's core heat comes from radioactive decay and primordial energy, not nuclear fusion.

Final answer: D