a.[B]

1. 北極的，南極的；極地的
2. 極的；極性的；磁極的；電極的
3. 正好相反的，截然對立的
   The two systems of government are polar opposites.

   這兩種政體截然相反。

adj.

1. relating to a pole or poles, in particular the North or South Pole or their adjacent area.
2. Physics  & Chemistry  having an electrical or magnetic field.
3. directly opposite in character or tendency:
   polar opposites.

n.