Question

When you read carefully in order to determine the meaning of a challenging word, you are

Answer 1

You are using context clues. Taking pieces of other parts of the sentence to figure out what a certain word means.

Answer 2

Well, this  answer can be many things! I would say "When you read carefully in order to determine the meaning of a challenging word, you are 'using context clues'", perhaps? Maybe not...how about "...using prior knowledge"? Since you didn't offer any alternative answers, or list any answers, I can only guess. I hope I helped you a little bit!