Final answer:
The climax in Act III of Hamlet occurs in the 'Closet Scene' when Hamlet confronts his mother and accidentally kills Polonius.
Step-by-step explanation:
In Act III of Hamlet, the climax occurs in Scene 4, which is commonly referred to as the 'Closet Scene' or 'The Nunnery Scene'. In this scene, Hamlet confronts his mother, Queen Gertrude, about her marriage to his uncle, Claudius. During this intense confrontation, Hamlet accidentally kills Polonius, who is hiding behind a curtain. This event marks the turning point in the play as it leads to a series of events that shape the resolution of the central conflict.