to protect them from the siren's song, circe advises Odysseus to?

plug his men's ears and have them tie him to the mast
journey to ithaca by way of the underworld
go back to aeolus & aovid the sirens together
cover himself with magic ointment

The correct answer is to plug his men's ears and have them tie him to the mast. In Book 12 of Homer's "Odyssey," Circe warns Odysseus about the irresistible lure of the sirens' song. She instructs him to instruct his men to tie him tightly to the mast of the ship and to plug their ears with wax. This way, they can all safely pass by the sirens while Odysseus can still experience their enchanting song without being drawn to his doom.