Final answer:
During the 'Mousetrap' play in Shakespeare's 'Hamlet', Claudius shows signs of guilt and discomfort, leading him to leave the room abruptly. This confirms Hamlet's suspicion of the King's guilt, aligning with option C.
Step-by-step explanation:
In Shakespeare's Hamlet, Claudius demonstrates a significant reaction during the 'Mousetrap' play. The play within the play is a strategic move by Hamlet to try to catch the conscience of the king, based upon the idea that the performance of a crime similar to one that a person has committed might provoke a response that reveals their guilt. In the pivotal moment of the performance, Hamlet observes Claudius closely, and upon witnessing the scene that mirrors his own regicidal crime, Claudius's reaction is one of visible distress. This is captured when Claudius rises and abruptly leaves the room in a fit of agitation.
The correct answer to the question regarding what action Claudius takes when watching the 'Mousetrap' play is that he shows signs of guilt and discomfort, eventually leading to him leaving the room shortly after the play strikes too close to home, thus terminating the performance. His reaction speaks to the underlying themes of guilt, performance, and reality in the play, as well as to the efficacy of Hamlet's plan to use the play as a means to reveal Claudius's true nature. Through this, Shakespeare also explores the concept of art reflecting life and the power of the theater as a mirror to our own actions and conscience.
In essence, when watching the 'Mousetrap' play, Claudius's actions align with option C: He shows signs of guilt and discomfort.