The correct answer is A) folkway.
Sue uses her laptop to look at Facebo*k during lectures instead of paying attention to class. She has violated a folkway.
In society uses and customs, a folkway is an informal rule of behavior. In this case, Sue is expected to pay attention to the teacher and participate in the class. That is the folkway. If she doesn't, she is violating a folkway that has no legal consequences but it is not well accepted in society.
The other options of the question were B) law. C) taboo.