Answer:
C. Personification
Step-by-step explanation:
Personification is a figure of speech that you can find in a piece of writing whenever an object, idea, abstract concept, aspect of nature, emotion or any event is given humans characteristics (such as thinking, talking, playing, throwing a ball, etc.).
Therefore, in the excerpt, the author uses personification as he or she talks about the pebbles and the waves as they were living things who perform actions that are characteristic of humans: The pebbles roar and the waves draw the pebbles back, fling them, return them, and they "Begin, and cease, and then again begin".