I believe the answer is language but I may be wrong.
I think it would be D or B. The tone is mysterious, which seems pretty close.
I think Macbeth is more anxious about murdering King Duncan. He becomes paranoid in the moments leading up to him killing the King, such as hearing spirits saying that he has "murdered sleep" and cannot speak the name of God. He hallucinates a dagger, as well and is only really able to produce enough courage to kill King Duncan when Lady Macbeth pressures him into doing it, calling him cowardly.
Lady Macbeth also says to Macbeth that if he is too scared to kill Duncan, she will do it herself. Shakespeare writes Lady Macbeth as a ruthless character, and she doesn't show much anxiety over killing Duncan.
