Answer:
C) personification
Explanation:
Personification is a literary device 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.). The provided sentence uses this type of device when giving the spheres (non-human, an object) the human attribute of being at play, as if they had the consciousness and will to perform such act as humans do.
