The Andromeda Spiral Galaxy Is Almost Edge-On to Us

Multiple Choice

The Andromeda spiral galaxy is almost edge-on to us. Astronomers have detected the orbital motion of this and other such galaxies' disk material by

A) using Hubble's law.
B) the big bang theory of 3-Kelvin radiation.
C) the steady state theory.
D) measuring Doppler shifts of different parts of the disk.
E) watching the stars travel around the nucleus back to where they started.