•Question 11   (1
 point) One fundamental requirement for an object to be a good
 tracer (i.e. marker) of the galaxy's spiral arms
 is that it be
   a.moving with small
 radial velocity (relative to earth).   b.moving
 with large radial velocity (relative to earth).   c. a short
 lived and therefore young object.
   d. a very long lived and therefore probably old
 object.    
  
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