The energy in the sun is generated mainly by:

The correct answer is Option (2) → fusion of hydrogen atoms

The sun’s core is at a temperature of the order of \( 10^{7}\,\mathrm{K} \). At this temperature hydrogen nuclei (protons) have enough energy to overcome their mutual repulsion and fuse into helium, releasing energy in the proton-proton cycle. Hydrogen is the fuel of the sun.

NCERT (2026-27):
Nuclear Fusion – Energy Generation in Stars – “… Thermonuclear fusion is the source of energy output in the interior of stars. … The fusion reaction in the sun is a multi-step process in which the hydrogen is burned into helium. Thus, the fuel in the sun is the hydrogen in its core.”