The best answer would be letter A. Across the sky
Among all of the given choices, it's the phrase that could be interpreted in the most literal sense.
Option B- Stars rocketed could be literally imagined but it can be a form of hyperbole. It can be an exaggerated expression.
Option C- This is also another phrase that could have a literary device.
Option D- Another figure of speech
So, Option A is really the correct answer.
A prepositional phrase is a group of words that lacks either a verb or a subject, and that functions as a unified part of speech. It normally consists of a preposition and a noun or a preposition and a pronoun.
This is an "object to category" relationship.
Dog belongs to the category "mammal," and snake belongs to the category "reptile."
They change shape due to a number of reasons.
The easiest reason to understand why they change is that they erode.
The coasts around the the world erode due to waves hitting cliffs, the wind batting against the coasts etc. Over a long period of time we can see that they change in shape.
(sorry I don't know why they move)