The correct answer is: "because people shift goals throughout life, identity achievement isn't final in the twenties"
According to the psychologist, James Marcia, adolescents go through four distinct stages of developing their sense of identity. The fourth and final stage of identity development is identity achievement. Marcia states, that identity achievement occurs when an adolescent commits to a certain sense of identity (which is fairly permanent). However, critics of this theory critique it by stating that identity achievement is not necessarily concrete and finalized during adolescence or one's early 20s. This is because people's goals shift throughout life,which in turn can change their identity even beyond their 20s all the way up to middle and late adulthood.