STRANGE:GROTESQUE::

a. sporadic:constant
b. naughty:malevolent
c. blue:azure
d. prudent:careful

I know the answer isn't "a" but I cant pick between b, c, and d because they all have a synonym relationship just like the analogy in caps.

Grotesque is an extreme of strange. Most strange things aren't grotesque.

Be sure you understand the meanings of all of the words.

Can you make a decision now?