When We Measure the Broadening of Absorption Lines in the Spectrum

When we measure the broadening of absorption lines in the spectrum of an elliptical galaxy, we can infer

A) the amount of gas and dust in the galaxy.
B) the mass of the black hole at the galaxy's center.
C) how fast the stars in the galaxy are moving relative to one another.
D) the galaxy's rotation curve.
E) how quickly the galaxy is forming new stars.