When adolescents first enter formal operations, they may have difficulty distinguishing their thinking about their own thoughts from their thinking about the thoughts of others. piaget would have argued that this results in a distinctive kind of adolescent

Egocentrism.

Explanation:

In Jean Piaget´s theory of cognitive development, the formal operational stage starts around twelve years old and is when adolescents become able to apply abstract thinking, without requiring concrete manipulation.  

Adolescent egocentrism is how they process social matters, as they are still incapable of distinguishing their own understanding from other people´s reasoning.

the right answer is a