1. "The fast runner ran fast during the race."
I chose this because it perfectly demonstrates how the same word—fast—can change its part of speech based on what it is describing.
The: Article (Adjective)
Fast: Adjective (describing the noun "runner")
Runner: Noun (the subject)
Ran: Verb (the action)
Fast: Adverb (describing how the runner ran)
During: Preposition (showing the relationship between the running and the time)
Race: Noun (the object of the preposition)