She fears reprisal, and when she is in the court preparing to tell the truth about Abigail, she ends up showing signs of being manipulated. Her testimony also shows that she finds many things threatening, and these threats cause her testimony to be highly inconsistent.
I would say that D) Fair is foul and foul is fair - best illustrates Shakespeare's use of foreshadowing in Macbeth. It says what is going to happen - not all is what it seems.
