Answer:
Keanon loves biking, snowboarding, and hiking.
Step-by-step explanation:
This sentence contains correct parallel structure because it uses three identical grammatical forms (gerunds) as objects of the verb 'loves': biking, snowboarding, and hiking. That's parallelism.
The other sentences use different grammatical forms (gerunds and infinitives) as objects and, therefore, cannot be considered parallel in structure.