In Jean Piaget's theory of cognitive development, which of the following is considered the most important and mature characteristic of the 'Formal Operational Stage', establishing children's capacity for abstract thinking and the creation of logical hypotheses?

According to Jean Piaget's theory of cognitive development, the 'Formal Operational Stage', starting around 11 or 12 years of age, marks the onset of high-level abstract thinking in adolescents. The most specific feature of this stage is 'hypothetico-deductive reasoning', under which adolescents can logically test various possibilities and hypotheses to solve a problem. Along with this, they become capable of drawing mental conclusions based solely on propositions without the presence of any concrete objects.