Answer:
D. hyperbole
Explanation:
Let us briefly define all the given answers.
Metaphor is a type of comparison, where the features and qualities of one thing are expressed through another familiar thing.
Onomatopoeia is a word formed from the sound it makes (splash, bam, bang).
Oxymoron is a combination of contradictory words that sound paradoxically (an open secret).
Hyperbole is a literary device that uses exaggeration to emphasize a message.
In the given example, it is obvious that the narrator didn't walk a million miles, but uses the exaggeration to show that the road to get there was as hard as if he really walked a million miles.
