Final answer:
Intragenerational mobility refers to the changes in an individual's social status within their own lifetime. The correct example illustrating this concept is an executive belonging to a different class than her parents.
Step-by-step explanation:
The concept of intragenerational mobility refers to the changes in social status that a person experiences within their own lifetime. Looking at the provided options, the only scenario that exemplifies this concept is:
b. An executive belongs to a different class than her parents.
This example clearly shows a change in social class from the class of the individual's parents, indicating a move within the social hierarchy during the person's life, thus representing intragenerational mobility. The other options describe conditions where the social class is shared with other relatives or doesn't show a change within the person's lifetime.