The Object You Are Observing Through a Telescope Appears Visually

Multiple Choice

The object you are observing through a telescope appears visually to be a single star,but you know by looking at its spectrum that it is a binary system.Which spectral feature might NOT characterize it as a binary?

A) The spectrum includes spectral lines associated with two different spectral types.
B) The sets of spectral lines move periodically to slightly higher frequencies and then slightly lower frequencies.
C) As the lines from one spectral type are moving toward higher frequencies, the lines from the other spectral type are moving toward lower frequencies.
D) The spectral lines from one spectral type become periodically brighter, while the lines from the other spectral type become dimmer.