Big bang nucleosynthesis yielded primarily a. light elements with atomic numbers less than 5. b. all 92 naturally occurring elements on the periodic table. c. light elements of atomic numbers less than 15. d. heavy elements with atomic numbers greater than 25.

The correct answer out of the four given options is

option a. light elements with atomic numbers less than 5

Explanation:

Big Bang nucleosynthesis, abbreviated as BBN, also known as primordial nucleosynthesis took place after the Big Bang for about 10 s to 20 minutes and resulted in the yield of isotopes of helium-4  (), helium-3 () which accounts for most of the world's helium, other isotopes of hydrogen in small amounts like deuterium (D or) and lithium isotope, lithium-7() in small amount.

Apart from these stable nuclei, it also yielded two radio-active isotopes: tritium() and beryllium-7() which due to their unstability later decayed into () and ().

All of these isotopes are of light elements with atomic number less than 5.