Abner, a 70-year-old retired teacher, feels that his life has not been of any real value or significance. according to erikson, abner has failed to achieve a sense of

Integrity

Explanation:

Erik Erikson was a psychologist who developed a theory of psychosocial development. According to this theory, people go through a series of different stages, in form of crisis, along their whole lifespan.

The eight stage in this theory is called "Ego integrity vs. despair" and it takes place after the 65 years of age and ends at the moment of death. During this stage, people contemplate their accomplishments and look back at the life they lived. When people do this and see their lives as unproductive or feel that they didn't achieve their goals, they become dissatisfied and develop despair. On the other hand, if they feel happy with the life they lived, they feel at peace and achieve a sense of integrity.

In this example, Abner is 70 years-old and he feels that his life has not been of any significance. Therefore, he is not feeling happy with the life he lived and has failed to achieve a sense of integrity and, on the contrary, he's feeling despair.