Although bound to impose the law, a judge is free to use her discretion to……the anachronistic……of some criminal penalties.
A) enforce … judiciousness
B) impose … legality
C) exacerbate … severity
D) mitigate … barbarity
E) restore … impartiality

:-s Need your hands on this question again.
I would go with D.

"Mitigate something" is "make something milder/more gentle".

I think you have to look at the thrust of the statement here, and determine which choice best completes the thought. Which choice best illustrates the more complete description of a
judge's position? The process of elimination may be the way to arrive at it. I have my own favorite, but then...