The Spectrum of a Very Distant Source Shows Spectral Absorption

Multiple Choice

The spectrum of a very distant source shows spectral absorption lines of ionized helium, He II, and molecular absorption bands from titanium oxide, TiO. What could one conclude about this star?

A) The source is probably the spectrum of a binary system, two stars close together, a hot star and a cooler companion, unresolved as separate stars from Earth but contributing separate spectra.
B) The source must have a very hot atmosphere containing helium gas overlying a much cooler stellar surface.
C) The source must have a thick, cool atmosphere overlying a hot stellar atmosphere.
D) There must be cool, interstellar gas containing TiO between the star and Earth.