Reading Comprehension (RC) | Re: After evidence was obtained in the 1920s that the universe

Could someone please comment on 117 regarding answer D ?

if the density of the "observable universe" (defined in the passage as "luminous matter in the form of galaxies")com[ing] to a small fraction of the[necessary 3 hydrogen atoms/cubic meter] forms the basis for the assertion that "there must be enough INVISIBLE (nonluminous) matter in the universe to exceed the luminous matter by a density by a factor of roughly 70", then wouldn't this density estimate of the observable universe being understated (as