Final answer:
Intergenerational mobility describes the movements in social class across generations within a family, whether upward or downward.
Step-by-step explanation:
The correct answer is option 3) Intergenerational mobility. This term refers to the upward and downward movement in social class by family members from one generation to the next. For instance, an upper-class executive whose parents belonged to the middle class and whose grandparents were part of the lower class demonstrates this concept. Intergenerational mobility is an important aspect of social stratification as it shows the shifts in social class across different generations within a family.