Final answer:
The professor used an informal negative sanction to maintain social control by asking the student to turn off her cell phone during class.
Step-by-step explanation:
When the professor stops the lecture and asks the student to turn off her phone, this is a form of informal negative sanction. Informal sanctions arise naturally out of social interactions and are not officially legislated or enforced through formal institutions. In contrast to formal sanctions like being expelled from school or receiving a promotion at work, informal sanctions can be simple gestures or comments that show disapproval or approval of someone's behavior. The professor's request for the student to respect others by turning off her cell phone is an example of using social control to maintain a conducive learning environment for all students.