Mallory, a single 23-year-old, has moved back into his parents' house after graduating from college so that he can afford to pursue a full-time graduate school program in business administration. his situation best illustrates a life phase called:

It illustrates a life phase called emerging adulthood.

Explanation:

This is a stage proposed by Jensen Arnett. It happens around 18-25 years of age.

Emerging means becoming prominent; in this case emerging adulthood refers to the period of time between adolescence and young adulthood. It is part of the developmental stages in which the individual explores and forms his/her identity, before making any long-term commitments.

In this case, Mallory is 23 and she is focusing on pursuing a full-time graduate school program, looking to form her identity and figuring out what to do in the long-term.

It can be deduces that she is in the emerging adulthood stage.