Final answer:
In 'Macbeth', the negative aspect of excess is primarily represented by Lady Macbeth's excessive ambition for power and the witches' prophecies that fuel Macbeth's ambition, both resulting in the disastrous consequences of their actions. The correct option is A.
Step-by-step explanation:
In Act I of Macbeth, the idea of excess manifesting as something negative is best exemplified by Lady Macbeth's ambition for power. Her insatiable desire for power and status leads her to manipulate Macbeth into committing regicide. In her famous speech, Lady Macbeth questions Macbeth's courage, equating his love for her with his willingness to seize the crown by any means necessary. This manipulation is steeped in the theme of excess; she is not content with their current status and craves more power, regardless of the moral cost.
The witches' prophecies also play a key role in the narrative of excess and ambition. Initially presented as a form of success, the witches plant the seeds of Macbeth's downfall by prophesying his rise to power. This prophecy fuels both Macbeth's and Lady Macbeth's ambition, leading to a series of violent and ruthless acts. The prophecies are tantalizing but deceptive, offering success that ultimately proves to be destructive.
In contrast, Macbeth's loyalty to King Duncan and Banquo's concern for Macbeth does not fit the theme of excess and its negative outcomes.