The sentence that uses the underlined word correctly is, Her grades on spelling tests are often good. The correct answer is option B. Why "good" and not "well"? The word "good" is an adjective. An adjective modifies a noun. The word "well" is an adverb. An adverb modifies an adjective, a verb and an adverb. In the sentence above, the word modified is "grades" which is a noun. Therefore, an adjective should be used, which is "good".