Read line 15 from the passage from the odyssey: “some demon calm’d the air and smooth’d the deep.” what does the line describe?

I would go with C .The weather has suddenly changed. The line describes the sudden calming of the seas. Before this line the ships were blown and tossed about to keep them from arriving in Ithaca. A demon is thought to be in control of the wind and seas because, for Odysseus, only a demon could be keeping him from his home. Also this "demon" has moved the ships to be tempted by the sirens.

it is an infinitive phrase with a subject.