Question

which conclusion did quantum scientists draw from excited hydrogen atoms always producing the same line - emission spectrum despite the amount of energy added?

hydrogen can exist only in the ground state.
hydrogen does not release photons.
hydrogen releases photons of light at only certain energies or specific wavelengths.
hydrogen has no electrons.

Explanation:

When hydrogen atoms are excited, electrons move to higher - energy levels. When they return to lower levels, they release energy in the form of photons. The fact that excited hydrogen atoms always produce the same line - emission spectrum (a set of specific wavelengths of light) despite different amounts of energy added implies that hydrogen releases photons of light at only certain energies or specific wavelengths. Hydrogen can exist in excited states (so “Hydrogen can exist only in the ground state” is wrong). Hydrogen does release photons (so “Hydrogen does not release photons” is wrong). Hydrogen has one electron (so “Hydrogen has no electrons” is wrong).

Answer:

Hydrogen releases photons of light at only certain energies or specific wavelengths.