Final answer:
The adolescent who is most developed in terms of Marcia's identity statuses is Identity achievement.
Step-by-step explanation:
In terms of Marcia's identity statuses, the adolescent who is most developed has the identity status of Identity achievement.
According to Marcia's theory, identity achievement occurs when an adolescent has successfully explored different options and has made commitments to a set of beliefs and values.
This means that the adolescent has gone through a period of exploration (Moratorium) and has actively considered different identities before making a commitment.