Answer: When you look at the other words in the sentence in order to determine the meaning of a challenging word, you are using context clues.
Explanation: Context clues are words, phrases or clauses that help the reader to figure out the meaning of an unknown word. Generally, these context clues are found in the same sentence in which the difficult word is; however, they may also appear in the following sentences. Two types of context clues are synonyms and antonyms. In that way, the option that completes the sentence provided is "using context clues".