Final answer:
In 'Twelfth Night,' Sebastian and Viola do not think any of the provided options; they are simply unaware the other is alive. The comedy arises from Viola's male disguise and mistaken identities when Sebastian arrives. They only discover each other's true fate at the play's end.
Step-by-step explanation:
Prior to the resolution of 'Twelfth Night,' both Sebastian and Viola are unaware that the other has survived the shipwreck they were involved in. They do not believe any of the options provided in your question; they do not think of each other as enemies, as unrelated individuals who are twins that have lost touch, nor do they think they are the same person in disguise. Instead, they are each living their separate lives in Illyria with the false belief that the other has perished.
In the play, Twelfth Night, much of the confusion and comedic elements arise due to Viola disguising herself as a man named Cesario. During the course of the play, Viola's twin brother, Sebastian, arrives in Illyria, leading to a series of mistaken identities and comedic circumstances due to their striking resemblance to each other. It's not until the end of the play that they are reunited and the truth of their identities is revealed to the other characters, resulting in the resolution of the various misunderstandings.
Learn more about Twelfth Night