When we see that a spectral line of a galaxy is broadened, that is, spanning a range of wavelengths, we conclude that
Answer
A) we do not have very good resolution of a star's orbital velocity.
B) there are many stars traveling at extremely high orbital velocities.
C) there are different Doppler shifts among the individual stars in the galaxy.D) we are actually measuring the orbital velocity of a cloud of atomic gas.
E) we are actually measuring the orbital velocity of dark matter.
