Final answer:
Young adulthood in the U.S. is a stage marked by identity formation, where individuals complete their education, start careers, and form intimate relationships.
Step-by-step explanation:
The text points out that in the U.S., young adulthood is a period where certain significant life events are expected to take place. It is during this stage that many individuals complete their education, start their careers, and often form intimate relationships. Within this context, Option 2: Identity formation is prominent, is the most fitting answer as it encapsulates educational, career, and personal development which are characteristic of this life stage. This period is crucial for setting the foundation for future stability and well-being, and as such, it is a time when individuals are encouraged to explore their interests and commit to long-term goals.