Not flashback because they are not reliving an event from the past, not tension because there is no conflict and not parallel because the ghost is not having similar actions happen to him as with the characters. so its surprise.
A prepositional phrase has to start with a preposition, and the only option here which starts with one is D, 'during the darkest night', where 'during' is a preposition.
The author used verbal irony as a literary device.
I would say b. Time, d. Location, and f. Atmosphere.
