:

 A.  More numbers on the list are in the class interval
     from 5 to 10 than in the one from 10 to 20.

 B.  The class interval from 10 to 20 is more crowded than
     the one from 5 to 10.
  
:

 a.  A and B are both true
 b.  A is true and B is false
 c.  A is false and B is true
 d.  A and B are both false