The Spectrum of a Star Shows an Equivalent Set of Dark

Multiple Choice

The spectrum of a star shows an equivalent set of dark absorption lines to those of the Sun,with one exception: Every line appears at a slightly longer wavelength,shifted toward the red end of the spectrum.What conclusion can be drawn from this observation?

A) The star is moving rapidly toward Earth.
B) A cloud of dust surrounds the star and absorbs the light.
C) The star is moving rapidly away from Earth.
D) The temperature of the star's surface is higher than that of the Sun.