Answer:
The correct answer would be, Leah is at a stage of concrete Operations and has demonstrated reversibility.
Step-by-step explanation:
According to Piaget's theory of cognitive development, there are different stages of development in the life of a person from childhood to adulthood. The third stage of Piaget' theory of cognitive development starts from the age of 7 years and lasts till the child reaches 11 years of age. In this stage, the child has most likely developed the logical thoughts. The brains starts to accept logical thoughts and reasoning.
So because Alex is 6 years old and has still not developed the concrete operations, he is least likely to remember the process of putting back the craft to its original shape, whereas Leah has developed such concepts and can easily remember the process of taking apart and putting back of the craft. So she demonstrated the reversibility process quite easily.