The coming of “birnam wood to dunsinane” could be described as

Aa hallucination.
Ba symbol of guilt.
Can army's use of camouflage.
Da nightmare.

Verified Answer :

both c and d depending on the point of view; Malcolm's army uses it as camouflage and it is one of the things that the witches say will happen before Macbeth's death so it is his worst nightmare.