In this passage from Macbeth, the mention of the owl can be interpreted in several ways. The most relevant interpretation among the given responses is:
Lady Macbeth is beginning to lose her sanity and only thinks she hears an owl shrieking.
This interpretation aligns with the overall themes of guilt and psychological turmoil present in the play. The owl, often associated with death and foreboding, symbolizes the dark actions that are taking place (the murder of King Duncan) and reflects Lady Macbeth's internal conflict and descent into madness as the weight of their crime begins to manifest.