If a Certain Star Shows a Strong Absorption Spectrum in Hydrogen

Multiple Choice

If a certain star shows a strong absorption spectrum in hydrogen Balmer lines, the surface temperature of the star is hot enough that

A) virtually all of the hydrogen atoms are ionized.
B) many hydrogen atoms have electrons in the n = 2 energy level.
C) many hydrogen atoms have electrons in the n = 3 energy level.
D) many helium atoms have been converted to hydrogen atoms.