Final answer:
2) A traitor
The term 'serpent' in the given context refers to a traitor who betrayed and caused the death of someone's father and then usurped his position of power by wearing the crown.
Step-by-step explanation:
The phrase 'The serpent that did sting thy father's life/Now wears his crown' refers to 2) A traitor. In this context, the serpent is a metaphor used to describe someone who was deceitful and betrayed the trust of the speaker's father. This person not only caused the death of the father but also took over his position, which is signified by the wearing of the crown. Serpents are commonly used in literature and religious texts to symbolize deception and evil, as seen in the biblical story of Genesis where the serpent tempts Eve in the Garden of Eden.