Final answer:
Lady Macbeth's disturbed mental state is primarily caused by her ambition for power and the guilt from her actions, not by her childhood, supernatural influences, or romantic entanglements.
Step-by-step explanation:
The primary reason for Lady Macbeth's disturbed mental state in Shakespeare's play "Macbeth" is b) Ambition and guilt. While the text doesn't offer a backstory on Lady Macbeth's childhood, her ambitions for power and the subsequent guilt of the bloody actions she and her husband take to achieve that power are central to her emotional unraveling. Lady Macbeth's intense desires manifest in her persuasive and manipulative nature, pushing Macbeth to commit regicide. However, as the consequences of their actions grow, Lady Macbeth's initial steely resolve dissolves into madness, haunted by the guilt of their crimes, as seen in her famous sleepwalking scene.