Final answer:
Choice D, 'The windows were eyes with cataracts; we could not see the ocean,' best exemplifies a metaphor, by directly comparing windows to eyes with cataracts.
Step-by-step explanation:
The best example of a metaphor out of the given choices is D: The windows were eyes with cataracts; we could not see the ocean. A metaphor is a figure of speech that makes a direct comparison between two things that are not alike but have something in common without using 'like' or 'as'. In this case, the windows are directly compared to eyes with cataracts, suggesting that they are not clear and obstruct the view, without using 'like' or 'as', which would make it a simile.