Final answer:
The sentence "I traced the dog" contains one noun phrase, which is "the dog".
Step-by-step explanation:
In the sentence "I traced the dog", there is one noun phrase (NP). A noun phrase is a group of words that serves as the subject, the object, or the complement in the sentence and is centered around a noun. In this sentence, there is one noun phrase: "the dog". The word "I" is a pronoun, not a noun phrase. Therefore, the correct answer is that there is one noun phrase in the sentence.