Answer: THE LAW OF READINESS.
Explanation: The law of readiness states that learning happens when a learner has the willingness to learn. This is in response to the facilitating the stimulus between stimulus and response. For example, a piano player willing to learn a new piece is more likely to learn it faster than another that is less motivated.
This law clearly reflects all the actions and activities of Susan. She couldn't concentrate in class because of her thoughts, and so many other things.