Answer:
a. Establish a theory of probable cause.
Step-by-step explanation:
Heather now knows the cause, and She is quite experienced. She is now studying the cause, and she is trying to come up with the theory of probable cause now. And as she will be able to come up with the theory, the practical will follow, and she will be able to remove the fault then. And hence the correct option is as mentioned in the answer section.