Which of the Following Children Has Most Likely Reached the Concrete

Multiple Choice

Which of the following children has most likely reached the concrete operational stage of cognitive development according to Piaget's four stages?

A) Bart dislikes carrots and tells his mom that his friend Doug doesn't like carrots.
B) Sara imitates her mother's mouth movements and says,"Dad."
C) Pierre follows the steps of brushing his teeth and changing his clothes before bedtime.
D) Cori places the six colorful containers in order of size from smallest to largest.