Hello Sophuechait2,
Your answer would be:
C. Compare definitions for the word with its synonyms.
I believe this correct because if you don’t know the true definition of the word synonymous that are similar to this word might help you out.
~Rendorforestmusic
John is not Gabriel’s biological son.
To the person that deleted my answer, go ahead and read "The Rockpile" and you will get the same answer.