Answer is 3. "I know my hour is come".
In this scene, Brutus reveals Volumnius that he has visualized Caesar's ghost in two occasions at night, the first at Sardis and the last one at Philipi fields. He recognizes it as a message, and understands that the end is near. Eventually, by stating "I know my hour is come" he accepts his faith, to finally conclude it is best to sacrifice himself than to die under the attack of his enemies.