In Karim's Family, It Is Required That Cell Phones Be

In Karim's family, it is required that cell phones be locked in a drawer during dinner time. However, in Marco's family, cell phones are encouraged to be brought to the table and used extensively during dinner. This example illustrates that norms __________.

A) can be violated
B) can differ across different groups of people
C) can only be defined by the head of household
D) are a form of authoritative control