Answer:
The sentence that correctly uses parallel structure is: 3. I like skiing, guitar, and a walk in the woods.
Parallel structure involves using the same grammatical form for parallel or similar elements in a sentence. In this case, all the items in the list ("skiing", "guitar", and "a walk in the woods") are presented using the same structure, as gerunds or noun phrases.
In the other sentences:
- Sentence 1 does not have parallel structure because "running track is something she loves" does not match the structure of the other items in the list.
- Sentence 2 has parallel structure in terms of using a list of nouns, but the items are not in the same grammatical form.
- Sentence 4 also has parallel structure in terms of using a list of activities, but "a vacation" is not in the same grammatical form as the other items.
Therefore, the correct answer is Sentence 3: I like skiing, guitar, and a walk in the woods.