In the context of Child Development and Pedagogy, under Jean Piaget's theory of cognitive development, which of the following is the most prominent and specific psychological characteristic of the 'Formal Operational Stage'?

According to Jean Piaget's theory of cognitive development, the most prominent characteristic of the formal operational stage (approximately from 11 years to adulthood) is the development of the capacity for 'Abstract Thinking' and 'Deductive Reasoning'. In this stage, a child becomes capable of solving problems logically and scientifically based on symbols and ideas alone, without any concrete or direct material. 'Object Permanence' is a characteristic of the sensorimotor stage; 'Conservation and Classification' are characteristics of the concrete operational stage; and 'Symbolic play and egocentrism' are characteristics of the pre-operational stage.