In which of the following scenarios would a nuclear family likely become an extended family?

The best choice is the scenario where a grandparent moves in with the family, as this directly expands the nuclear family structure. A nuclear family typically consists of two parents and their children. When a grandparent, or any relative, joins the household, it creates an extended family dynamic, which includes additional relatives living together and sharing daily life.

In contrast, the other scenarios involve changes that do not result in a shared living arrangement. When children go away to college, they are temporarily leaving the home, which does not affect the immediate family structure. A parent getting a new job might alter the family's financial situation or schedule but does not impact the composition of the household. Similarly, going on vacation together, while it does foster family bonding, does not change who lives in the house or the family structure itself. Thus, the movement of a grandparent into the home is the key factor that transitions a nuclear family into an extended family.