Answer: D. Or art thou but/A dagger of the mind
Explanation: In this passage from Act II, Scene I of "The Tragedy of Macbeth" by William Shakespeare, the evidence from the text that leads the reader to believe that the dagger Macbeth sees is an illusion is "Or art thou/A dagger of the mind...". Before Macbeth kills Duncan he sees a dagger in the air. Its handle near his hand and its tip pointing to where Duncan is sleeping. Moreover, this dagger is full of blood. Macbeth gathers whether it is real or a creation of a confused mind.