In this sentence, the adjective “cautious” modifies the verb “flew.” Given that only adverbs can modify verbs, the proper word to use would instead be “cautiously,” which is an adverb. 

In this sentence, the adjective “gentle” modifies the verb “adjusted.” Given that adverbs can only modify verbs, the proper word would instead be “gently,” which is an adverb.

You can spot this sentence's error by realizing that the adjective "large" needs to be a noun because it is preceded by the definite article "the," which refers to nouns, not adjectives. Changing "large" to "largeness" would correct the sentence's error.

The word "real" here is meant to modify the adjective "soon," which means that an adverb is needed. The adverb form of the word "real" is "really," so the sentence should say, "I'm sorry that I'm running late for dinner," I said to my mother on the phone, "but I'll be home really soon." People might use the word "real" as an adverb during everyday conversation, but that slang form is grammatically incorrect.

This sentence's error is that it uses an adverb in the place of an adjective. "Badly," as an adverb, is referencing not the quality of the dog's odor, but its poor ability to smell.

This sentence has three subjects: "Sarah," "Emilie," and "Jenn." Because of this, the sentence requires a form of the word "both" that is used to refer to groups of three or more. "Both" would be correct if only two of the girls were racing.  However, since all three are racing, we need to use the adverb "all" instead of "both." The corrected sentence would read "Sarah, Emilie, and Jenn competed against one another in the four hundred meter hurdle event, and they all scored similarly."

The word "original" is an adjective and should modify a noun. Here, it modifies the verb "passed". An adverb would be correct: "Many popular books and movies are inspired by folktales that were originally passed down orally from generation to generation."

The word "good" is an adjective and should describe a noun. Here, it describes the verb "went" and is grammatically incorrect. Changing "good" to the adverb "well" corrects the sentence's error. The corrected sentence reads, "Despite the terrible dress rehearsal the night before, the opening performance of Romeo and Juliet went really well."

This sentence uses an adjective (“complete”) to describe another adjective (“wrong”). An adverb is the correct part of speech in this context. The corrected sentence reads: "Tom had a terrible sense of direction but a wonderful sense of humor; he consistently headed off in the completely wrong direction but laughed about it later."

In this sentence, the adjective “painful” is used to describe the verb “dragged on.” As adjectives only describe nouns and pronouns, "painful" contains the sentence's error, and the adverb "painfully" would be a grammatically correct choice. The corrected sentence reads, "May dragged on painfully; Dorothy was counting the hours until graduation, and they couldn’t pass fast enough."