Final answer:
The correct answer is option b. Lady Macbeth explains Macbeth's strange behavior at the banquet by attributing it to a condition he has had since youth which is related to stress, not mental illness or any wrongdoing.
Step-by-step explanation:
During the banquet scene in Shakespeare's Macbeth, Macbeth starts to act erratically upon seeing the ghost of Banquo. To explain Macbeth's behavior to the confused and scared guests, Lady Macbeth quickly intervenes. The correct explanation is given by Lady Macbeth in the lines:
"Sit, worthy friends, my lord is often thus,
And hath been from his youth."
This is option B that attributes his strange behavior to stress related to an ailment he has had since youth. She tries to reassure the guests that his condition is something quite normal and familiar to him, downplaying the severity of his outburst.