The head of the Sphinx once wore a headdress with a rearing cobra What is the significance of the cobra?

it was believed to give the wearer supernatural powers. it was believed to protect the wearer from evil forces. it was believed to make the wearer immortal. it represents the wearer's ability to "smite his enemies."

The significance of the cobra in the headdress of the Sphinx was that it was believed to protect the wearer from evil forces.