While Piaget Proposed That Formal Operational Thought Is Not Fully

While Piaget proposed that formal operational thought is not fully settled in until around 15 years of age,evidence suggests that some people never fully employ formal operational thinking.Studies show that only _________ of college students and adults achieve formal operational thinking,and other estimates run as low as _____.

A) 40% to 60%;25%
B) 30% to 50%;25%
C) 25% to 50%;10%
D) 50% to 75%;40%