What Is It That Makes the Study of the Structure

Multiple Choice

What is it that makes the study of the structure of the Milky Way Galaxy more difficult than that of much more distant spiral galaxies?

A) The galactic center is visible only from the southern hemisphere, where, until recently, no major telescopes were available for the study of galactic structure.
B) The Milky Way appears to be unique, with a structure quite unlike any other galaxy.
C) The Sun is within the Galaxy, and its motion confuses the interpretation of the motion of other parts of the Galaxy.
D) Most of the Milky Way is hidden behind dense gas and dust clouds in the galactic plane.