Which two elements overwhelmingly dominate the elemental composition of any given nebula by mass?

Answer

Hydrogen and Helium

The bulk of any nebula is composed almost entirely of hydrogen and helium, which together account for the vast majority of the mass and volume within these interstellar clouds.

Which two elements overwhelmingly dominate the elemental composition of any given nebula by mass?
SpaceastronomycompositionnebulaGases