Horatio is a developing child. In his math class, he is learning arithmetic. One day Horatio learns that 3 + 7 = 10 and also that 7 + 3 = 10. The next day, his teacher instructs Horatio that 6 + 9 = 15. Without hesitation, Horatio writes down the equation 9 + 6 = 15. Until recently, Horatio was unable to manipulate arithmetic equations in this way. With regard to Piaget's theory of cognitive development, what is Horatio's maturational stage? Question 40 options: Formal operational stage Concre