Answer:
A. Ghost.
Step-by-step explanation:
This is the excerpt from Shakespeare's "Hamlet" (Act-I scene v) where Hamlet learns that his father was murdered by Claudius and now has worn the crown. Therefore, after knowing this, he decides to plot revenge against him. He uses the metaphor of snake to display the evil side of Claudius. The supernatural element that has been emphasized here in this scene is the ghost who is his father's spirit as it reveals Claudius' evil side and at the same time puts some restrictions on Hamlet in order to pursue the revenge plot. The ghost requests Hamlet to comply with these restrictions. Thus, the supernatural element employed in this excerpt is a ghost (Hamlet's father's spirit) who is introduced by Shakespeare to provide a turning point to the main plot.