In analyzing Shakespeare's use of the dagger in Macbeth, the two interpretations that best explain its use are:
A. Macbeth's sight of the dagger, which is not actually there, indicates his insanity.
E. Macbeth's guilt for thinking about killing the king has triggered its appearance.
These interpretations highlight the psychological turmoil Macbeth is experiencing as he contemplates the murder of King Duncan. The dagger symbolizes his ambition and the mental conflict that arises from his contemplated actions, ultimately leading to madness and further guilt.