Final answer:
The view of the family as a productive unit providing for material needs is an economic standpoint of defining a family.
Step-by-step explanation:
The definition that views the family from an economic standpoint is: b. A productive unit providing for material needs.
Sociologists define a family not only by its structural composition but also by the roles it plays within society, including its economic functions. In the context of functionalism, families are seen as groups that perform essential roles for society, both internally and externally. For example, they provide for the material needs of their members and contribute to the well-being of society through production and consumption activities. As such, families can be considered economic units within the broader social structure.