Why is Macbeth both excited and fearful after hearing the witches' prediction about his future?

AThe witches told Macbeth that even though he would not be king, his children would inherit the throne.
BThe witches are powerful, and Macbeth is afraid they will do something to harm the king.
CThe witches told Macbeth that he would be a great hero even though he would be killed in battle.
DThe witches told Macbeth that he would be king, and he is worried about his role in making the prediction come true.